A few years ago I started collecting signed 8 x 10s of U of M football greats. I now have about 100. I don't have a mancave yet because I'm currently in a 2-bedroom condo, but we will be buying a house within the next year or so and sufficient mancave space is at the top of my checklist.
Relatedly, if anyone knows of a store that might sell some harder-to-find U of M autographs, please give a shout. I have a few holes in my collection (examples: Jarrett Irons, Jerame Tuman, Tripp Welborne), but they are proving hard to find. And yes, I am aware of eBay.