It's a tough brief. But one that every designer (myself definitely included) would love a crack at. The 2012 Olympics people have unveiled the new pictograms for the games. For me, the Munich '72 graphics have always set the standard, with Mexico '68 following closely.
There are two versions of these, the black and white ones at the top, and the 'dynamic' ones underneath. You can see the full sets over on the official 2012 website and read more about them on their blog.