So wouldn't it be nice if the first few pages of the photo gallery were not just "new" photos but photos that also are getting attention from other users.
Similar to the way trade topics resurface when they become relevant again, making photos "bump" with every comment would create interest in photo's that would have otherwise drifted off into the depths.
And since each user can only post once per photo, it's not like you'd have the same photos forever on the front pages. They'd just be there as long as they remain relevant or become relevant once again.
So if you like the idea, vote yes!