This site seems to have good pics and descriptions of nice fingerlime selections, and in general seems to be a true account of some of the possible wild types in my experience.
http://www.gourmetlimes.com/myftp/www.gourmetlimes.com/varieties.html

If you mix around the color/ flavor descriptions you could get an idea of some of the diversity of types, including perhaps some of the less pleasent possibilities that occur.