So, youre saying that I have to download the .apk, tear it apart, tweak what I want, and then rebuild it and install it? Hm... Are there programs to build .apk files for themes? Im so lost.....
Yep that's right. Take a look at apk manager (for windows). I have a mac but the only reason I have windows on my computer is for this program. It will allow you to take apart an apk (like a go sms theme) and modify any png to your liking or colors and compile it back together and sign it. It's got a really nice interface too so it's very user friendly. Let me know if you have any questions on how to use it and I'll be happy to help!