I'd like to be able to do the same thing. I posted a bit in a thread or 2 just a bit lower on this page. I'm running Mint 13 KDE but I suspect what I have learned pertains to all Linux desktops. There appear to be NO current up to date programs for theme creation in Linux as there are for Windows. It can be done, but (hey, other people do it) you will need to spend a lot of time understanding how it all fits together. Some of the theme stuff is written in c++ or QT. Some of the stuff is in .svgz files. I don't have all this organized in my head yet, but maybe over the next month or 2 it will start making sense. I hope you are serious about theme creation and some day write a great tutorial for the rest of us.
i5 3570k, ASRock z77 Extreme 4, 8 Gb Ripjaws 1600, Antec 430w psu, HVR 1600 tv tuner, custom case- marble top, oak face. Carver & DCM Time Window sound system. Mint 14 KDE.