Two suggestions I have, One, maybe under your profile there could be a spot for completed paintings (such as the bookmarked paintings tab)? I'm glad you added the check mark when a painting is completed but it might be nice to see all that information in one place. Second, how about adding a heart option to each painting that's uploaded? Similar to the evil Facebook. Sometimes I want to like certain paintings but right now the only way to do it is comment.
Keep up the great work Felix. I love the site and I'm glad to have stumbled upon it.