I have been working on some wiring mods for my 94 YJ lately, so let me share a couple ideas with you. These are some things I have learned to appreciate during my electrical adventures.
First of all, consider adding an auxiliary fuse block. The one I chose was Painless Performance Cirkit Boss (P/N 70107). I mounted this inside the jeep on the firewall next to the stock fuse panel. It has a combination of switched and continuous power circuits to work with. I like this because I don't have to try to tap into some other circuit for power. When I wire the circuit, I don't need additional fuses in the line... makes troubleshooting a lot easier when you don't have those hidden fuses to chase down.
A load like a compressor is too big to run from most switched power circuits themselves. This situation calls for a relay and ideally, a circuit breaker. If you need help with a wiring diagram, I can sketch one up and send it to you. You can use this same process for extra lights, power inverters, etc.