Here's a novel idea: ask gamers to recreate stage layouts and overworld maps from their favorite games... without any sort of reference! The result is Mapstalgia, a place where folks can upload hand-drawn game maps spawned entirely from memory for everyone to admire and comment upon. Some are more accurate than others, but it's still amazing how much detail some folks remember.
I've been thinking, what's more difficult? Redrawing maps from older games or newer ones? Certainly, the newer games are fresher on your mind, but there is so much more content than in those from, say, the 8-bit era. Plus, it's a lot harder to render a 3D space as an overhead view if the game itself doesn't include a 2D map screen.
I've attached a few samples to give you an idea of the range of submissions, and I urge you to hit up the site and upload your own. There are some truly impressive pieces, like the room breakdown from Castlevania: Dawn of Sorrow, as well as joke entries, like the single corridor that represents many modern FPSes. It's all in good fun!