Here is a script I put together to do batch file renames. Its written in Ruby and works on all platforms.

You can download it here

#Batch file rename/move script

Dir.chdir '/Users/username/Pictures/'
# sets destination folder

pic_names = Dir['/Users/username/Downloads/*.{jpg,JPG}']
# sets source folder

puts 'What would you like to call this batch?'
batch_name = gets.chomp

puts
print'Downloading ' +pic_names.length.to_s+' files: '
# this is the counter. 

pic_number = 1

pic_names.each do |name|

new_name = if pic_number <10
batch_name + '0' + pic_number.to_s + '.jpg'
else
batch_name + pic_number.to_s + '.jpg'
end

if File.exist?(new_name) == false
print ' .' # this is the progress bar
else
puts 'Error: ' + new_name + ' already exists'
exit
end

File.rename name, new_name
# renames the pictures

pic_number = pic_number +1
#counter increment

end

puts
puts 'Done bitches!