gistfile1.txt

class Admin::PicturesController < ApplicationController
  layout 'admin'
  admin_assistant_for Picture do |admin|
    admin.index do |index|
      index.columns :image
      index[:image].image_size = "75x75"
    end
  end
end

class Picture < ActiveRecord::Base
  has_attached_file :image, :styles => { :thumb => "75x75>" }

  belongs_to :gallery
end

class Gallery < ActiveRecord::Base
  has_many :pictures
end