The NFPA is the standards body that writes and maintains the national electrical codes that serve as a basis for most state electrical codes. In the NFPA code book 14 gauge wire is generally rated to carry up to 15 amps without overheating. Keep in mind the circuit breaker is there to protect the wire - not much else. So if you use 12 gauge on a 15 amp CB you're probably wasting a minuscule amount of money and copper, plus 12 gauge is stiffer and not as easy to work with. You could possibly use a 20 amp breaker and a 20 amp receptacle(s) an get a bit more ampacity for very little more money. I would recommend you get computer (data) or medical (hospital) grade receptacles though, as the $0.17 specials are pretty much garbage. Actually you can get a decent receptacle without even going that far, but watch out for the really cheap ones. Most 20 amp that I've seen were pretty good - the really cheapo ones are generally the 15 amp 'for someone elses house' type.

I'd strongly recommend you at least consult with a local electrician as local ordinances vary, and this could effect your safety and fire coverage.