Google them, Happy Gardening.
This way you'll have a number of sites that specialise in them and show pictures with the descriptions.
There are a number of them and i've bought from several of them.

There are a fair number of pictures under the "E" at the bottom of this page. Otherwise, I would just google "Epimedium" images, and you will probably find the catalogs of several online nurseries that carry a wide variety of this genus.

Kew Books publish an excellent monograph on Epimedium, though it does cost £42.

http://www.kewbooks.com/asps/ShowDetails.asp?id=260