Custom PNG as a button or panel background

hi guys!
I’v always had an obsessive idea to make blender look like XSI, since I think XSI’s interface is the most stylish and sexiest GUI any 3d-package ever had. As many of you know, Autodesk is killing Softimage, so now I have a great incentive and motivation to dig blender source code with intention to change buttons and panels appearance.
But before that I need to know if it even possible :slight_smile: Cause otherwise I’m “doomed” for month of digging with no results )
So what exactly I need is the ability to load custom PNGs as a button or panel background. What part of a source code should i inspect in the first place? Thx