I completed the game, but didn't get everything needed to "complete the masterpiece". I only missed one paint tube and one landscape, and I really don't feel like going through every level again just to grab those. BUT if it unlocks extra levels or something, I just might do it. So does anyone know if completing the painting actually does anything?
Just the achievement as far as I'm aware although it may unlock extra levels for the mini games. Check to see if any of those levels are still locked. As far as I'm aware though you can just select a chapter to replay to get anything you missed, rather than playing through the whole thing again.