WolframAlpha has compiled a growing list of portraits of iconic figures drawn by parametric functions. Some of them are surprisingly good – though, as Joe Hanson points out, there's a decent chance these functions are being churned out by a computer instead of an actual person, seeing as they are OBSCENELY complex. (Here are the parametric equations for the Einstein curve pictured up top, plotted for t from 0 to 152π. Yeah, have fun expressing those curves on your own.)
As of this posting, the list contains 142 named curves, though we wouldn't be surprised if more popped up in the future. We've grabbed a few of our favorites and included them below, but you can check out the whole collection over at WolframAlpha.