The unusual shape I've chosen for my symbol is a tesseract. It is the 4D equivalent to a 3D cube. It has 8 cube-sides, shown my diagram at left. If you look carefully at the central figure, you will see each one of them. I chose this form to represent my integrated design approach.

For more 4D thinking, check out these links:
geom.uiuc.edu page: Tesseract guided demo!
Wikipedia definition: Interesting image gallery