```ruby
Dir.glob("**/*.{jpg,gif,jpeg,png}").sort.each do |image|
name = File.basename(image)
in_use = false
Dir.glob("**/*.{erb,css,js,html,htm}").each do |file|
contents = File.read(file)
in_use = contents.include?(name)
break if in_use
end
if !in_use
puts "Deleting '#{image}'"
File.delete(image)
end
end
```