Bladewire's idea is nice, that looks modern and professional how customers expect things to look these days.
If you want a cheapie thing heres a Wordpress plugin for it
https://wordpress.org/plugins/hot-or-not/
I looked around for "Rate my photo" and "Hot or not" clone scripts but didnt see anything amazing, a lot of 3/5 star ratings. And theyre old so theyre probably not responsive. :/