Heh. You guys finally inspired me to get off my but and put up some pegboard in the safe. If you have one of the 5 gun sentry gun cabinets (Key lock only, bare bones) that cost about $100, there is a simple way to mount pegboard. The door has two strips of reinforcing steel welded onto the inside, with a 1" gap between the door and the inside of the reinforcing bar. (The bars run vertically). This leaves a perfect gap to install spacers, pegboard and some hooks. It's crude, but you can do it with leftover scraps of pegboard (or any other similar material. I almost used some leftover laminate flooring before I spotted the pegboard).
All you do is drill into the reinforcing bar, drop in drywall anchors, and cut your backing to size. I did it in about two hours, and the only power tool was the drill. Best part? I did it entirely with scraps. Big enough for two revolvers above the lock. Probably get 3-4 below it, depending on how far down you want to extend the mounting system.
I can't get pics up anytime soon, but it doesn't look quite as nice as the above systems. However, it is possible to do in one of these tiny gun cabinets ($100) if you have a small collection and a very small budget, but need more space for handguns. The "shelf" included in this cabinet was literally 4 inches deep by 9 inches wide. Can't really store anything on it. I ended up storing handguns in cases and stacking them in one of the rifle slots. This is much better now.