It should pretty simple to implement (mostly coding the HTML part of it I believe) since this sort of information is already available. It would be nice to have a simple URL for a given user's list of solved movies so we can share that with people and friends. Something like http://whatthemovie.com/username/solved, that would even render in an interesting URL like "what the movie caio1982 solved", for instance. Kudos to Internet searchs :-)

The list could use the already available films thumbnails. The username would be a <h2> tag or some higher number then a thumbnail on the left with the title of the movie on the right with a link to IMDB or Amazong (if available, of course). Below the movie title could be inserted the date when this specific movie has been solved by username. Simple like that: 1 row 2 columns, 1 movie per row!

For the sake of fun you can insert a confirmation link before listing these rows of films with title or even NOT to display the movies titles if the user viewing the page has NOT solved them already, maybe.