Create a WP site that allows users to create their own content (we use the Gravity Forms plugin).
Users will be posting two pictures, a before and after, and the pics will be displayed side-by-side so visitors can comment.
I'll buy whatever theme makes this easier to do so you don't have to start from scratch with a theme.
I don't do escrow and on small projects like this do not pay until project completion. Budget is $100 or less and any bids more than $100 won't be considered.