Here is an idea I came up with, but I don't think much of it. I figured I'd share it anyways. Lets say you've been playing the game for less then 2 hours, well it shows in your clothes. Once you've been playing the game for more then lets say 48 hours, maybe the clothing you wear looks dirtier, or has some blood stains or some holes in it. You show off your experience through clothes that represent the hours played in the game. The clothes wouldn't get so destroyed that your half naked, but rather a few tears and blood stains here and there.