Simple AppleScript to easily batch rename multiple files sequentially. GUI asks user to select files and input a name before renaming.

Batch File Rename.scpt

-- This code comes from https://gist.github.com/oliveratgithub/
-- Open in AppleScript Editor and save as Application
-- ------------------------------------------------------------
--this is required to break the filename into pieces (separate name and extension)
set text item delimiters to "."
tell application "Finder"
	set all_files to every item of (choose file with prompt "Choose the Files you'd like to rename:" with multiple selections allowed) as list
	display dialog "New file name:" default answer ""
	set new_name to text returned of result
	--now we start looping through all selected files. 'index' is our counter that we initially set to 1 and then count up with every file.
	--the 'index' number is of course required for the sequential renaming of our files!
	repeat with index from 1 to the count of all_files
		--using our index, we select the appropriate file from our list
		set this_file to item index of all_files
		set {itemName, itemExtension} to {name, name extension} of this_file
		--if the index number is lower than 10, we will add a preceding "0" for a proper filename sorting later
		if index is less than 10 then
			set index_prefix to "0"
		else
			set index_prefix to ""
		end if
		--
		--lets check if the current file from our list (based on index-number) has even any file-extension
		if itemExtension is "" then
			-- "" means there is no file-extension present.
			set file_extension to ""
		else
			--yup, we are currently processing a file that has a file-extension
			--we have to re-add the original file-extension after changing the name of the file!
			set file_extension to "." & itemExtension
		end if
		--let's rename our file, add the sequential number from 'index' and add the file-extension to it
		set the name of this_file to new_name & index_prefix & index & file_extension as string
	end repeat
	--congratulations for successfully accomplishing the batch renaming task :)
	display alert "All done! Renamed " & index & " files with '" & new_name & "' for you. Have a great day! :)"
end tell

Drag-n-Drop Files Batch Rename.scpt

-- This code comes from https://gist.github.com/oliveratgithub/
-- Open in AppleScript Editor and save as Application
-- ------------------------------------------------------------
--this is required to break the filename into pieces (separate name and extension)
set text item delimiters to "."
-- Let the App receive drag'n'dropped files
on open theDroppedItems
	-- build the file list based on the dropped files
	set all_files to every item of theDroppedItems as list
	tell application "Finder"
		display dialog "New file name:" default answer ""
		set new_name to text returned of result
		--now we start looping through all selected files. 'index' is our counter that we initially set to 1 and then count up with every file.
		--the 'index' number is of course required for the sequential renaming of our files!
		repeat with index from 1 to the count of all_files
			--using our index, we select the appropriate file from our list
			set this_file to item index of all_files
			set {itemName, itemExtension} to {name, name extension} of this_file
			--if the index number is lower than 10, we will add a preceding "0" for a proper filename sorting later
			if index is less than 10 then
				set index_prefix to "0"
			else
				set index_prefix to ""
			end if
			--
			--lets check if the current file from our list (based on index-number) has even any file-extension
			if itemExtension is "" then
				-- "" means there is no file-extension present.
				set file_extension to ""
			else
				--yup, we are currently processing a file that has a file-extension
				--we have to re-add the original file-extension after changing the name of the file!
				set file_extension to "." & itemExtension
			end if
			--let's rename our file, add the sequential number from 'index' and add the file-extension to it
			set the name of this_file to new_name & index_prefix & index & file_extension as string
		end repeat
		--congratulations for successfully accomplishing the batch renaming task :)
		display alert "All done! Renamed " & index & " files with '" & new_name & "' for you. Have a great day! :)"
	end tell
end open