I line the base, but I would love a brick wall with graffiti on it. I would be all about a custom base, but the stability of the base would worry me. Have there been any successful custom bases done?
Pathfinder has done some custom bases for X Men PFs. Not super complex but very good, they're Danger Room style, a BIG improvement over the ugly X and rocky bases. It's not that it's impossible to do custom bases, process is the same as every other custom piece... but bases are more expensive, both the initial investment and the final price are higher.