This script takes a directory of files ./A with broken aliases in ./A/B and fixes all those aliases by finding the associated file in ./[A-B] and calling `ln -sf`. It will not handle dir aliases, and can be confused when a the source tree contain multiple files with the target filename. As a bonus, this script will reduce the size of directories…

alias_fixer.rb

#!/usr/bin/env ruby                                                                                                                                                                                         
require 'fileutils'                                                                                                                                                                                         
                                                                                                                                                                                                            
# these are the folders containing all your images                                                                                                                                                          
if ARGV.size == 2                                                                                                                                                                                           
  dir_base     = ARGV[0]                                                                                                                                                                                    
  alias_folder = ARGV[1]                                                                                                                                                                                    
else                                                                                                                                                                                                        
  puts "usage $0 dir_with_all_files sub_dir_containing_broken_aliases"                                                                                                                                      
  puts "  or pass -d to use defaults:  ~/img  background"                                                                                                                                                   
  puts "  ATTN: this scrip will be confused by a source tree with A/alias_name.jpg and B/alias_name.jpg, where B/alias_name.jpg is the correct target"                                                      
  if ARGV[0] && ARGV[0] == '-d'                                                                                                                                                                             
    dir_base     = File.expand_path '~/img'                                                                                                                                                                 
    alias_folder = 'background'                                                                                                                                                                             
  else                                                                                                                                                                                                      
    exit                                                                                                                                                                                                    
  end                                                                                                                                                                                                       
end                                                                                                                                                                                                         
                                                                                                                                                                                                            
alias_path = File.join dir_base, alias_folder                                                                                                                                                               
                                                                                                                                                                                                            
# list of all alias file paths, dirs excluded                                                                                                                                                               
alist = Dir.glob( alias_path+'/**/*').                                                                                                                                                                      
            select{|w| w.scan('.').any? }                                                                                                                                                                   
                                                                                                                                                                                                            
puts "I will try to update #{alist.count} aliases"                                                                                                                                                          
                                                                                                                                                                                                            
# a list of all file paths, alias fodler contents excluded                                                                                                                                                  
flist = Dir.glob( dir_base+'/**/*' ).                                                                                                                                                                       
            reject{|w| w.scan(alias_path).any? }                                                                                                                                                            
puts " from #{flist.count} source files"                                                                                                                                                                    
                                                                                                                                                                                                            
# forcably create new aliases by overwriting old files                                                                                                                                                      
alist.each do |f|                                                                                                                                                                                           
  flist.each do |w|                                                                                                                                                                                         
    if w.split('/').last == f.split('/').last                                                                                                                                                               
      FileUtils.symlink(w, f, :force => true)                                                                                                                                                               
      puts "linked #{w}  to  #{f}"                                                                                                                                                                          
      next                                                                                                                                                                                                  
    end                                                                                                                                                                                                     
  end                                                                                                                                                                                                       
end     

Note the nifty /usr/bin/env ruby gleaned from here