Want to see every engine cowling design known to man? Check out the Amateur Built aircraft page at 1000aircraftphotos.com. Lots of pictures of rare homebuilts (including stuff like the Stit's Flut-R-Bugs and the Marquart MA-5 Charger). Worth taking a look at, and always a good resource for "I know this plane exists, but what does it look like?" sorts of questions.