Man caves tend to be decorated with poorly hung sport plaques, bad movie posters, and fat heads stuck on the walls. Guys, THERE IS A BETTER WAY!
Rule #1: Frame that shit! Get a basic matte and matching black or white frames (a trip to ikea is cheap and easy). By framing everything the same, it ties all your different teams and interested together.
Rule #2: Take the extra time time to find well designed art that represents your sports teams, movies you love, and interests you have. It's often funnier, more interesting and way cooler looking than the standard stuff you'll find in a store. There are super cool designers and artists out there who are just as into all the stuff you are and have found awesome ways to show it off.
Rule #3: Please measure and lay it out before you hang it, do it on the floor, or check out this quick tutorial on how to lay out a gallery wall. At the very least, center it and make sure it's level! The women in your life will be way more impressed and likely to hang out with you in "your room" if it's moderately thought out.
Here are some great examples and places to find some awesome MAN ART.
Stadium Prints, United Steaks of America, Tatooine, 40 Year Old Virgin, Beer Chart