sorry you didnt make it clear what you wanted.
if you want to use a graphics library then open gl and glut would be quite easy. again im not sure this is what you want but check out http://www.videotutorialsrock.com/
also maybe wxWidgets
This GUI (and a lot more) C++ platform offers Linux/Windows/Mac portability. I think one of the Adobe Photoshop products use it for their GUI. It was recently released on the Lesser Gnu Public License (LGPL) which means this toolkit can be used for commercial applications without royalties or per-developer fees. I'm pretty sure most of what you have to do is just not statically link your product (ship DLLs with it).