Theres probably a million or so solutions to this problem. Some will get you sued, some won't. The simplest solution I've come up with myself is quite frankly to just change the image. Personally I've never been a big fan of apparel with pac's face on it. I always thinks it looks rather cheesy in the end. My suggestion is that you go with something that scream 2pac, but isn't 2pac per se. For instance... the black and white logo at the top of the main 2pacboard page is an excellent start. It's not tupac, yet anyone in the know will know exactly who it is. Changing up the design of that type of print would get you some varience and yet keep Amaru off of yor back. Furthermore, I personally would like to see something with like a bandana tied in front like pacs hanging off o the letter "T" in tupac. And if you wanted to get further into it, hell even add dripping blood or something like that... fans of 2pac will know what the hell your referring to, and will "get it" and you won't have to deal with the hassles of using a likeness. (Which, yes is copyrightable.)
My last bit of advice for you though is to just be carefull... Your marketing these in america, the same country that allowed Paris Hilton to copyright the phrase "thats Hot". Keep that in mind, because if someone can copyright a spoken phrase commonly said millions of times prior to it's copyright, then you better believe just about any visual image can be copyrighted as well.