Change stock artist photo on Ipod Touch

Hello. I am a new owner of an Ipod Touch and have a question for y'all. I uploaded all of my songs and I see that on the ipod, the artists pictures are either a random album cover or a stock photo that Apple provides. The only issue that I have is on one particular artist, a giraffe is randomly used as a stock photo and would like for it to be changed since it is completely irrelevant to the artist! I don't see the giraffe picture anywhere on Itunes on my PC. Is it possible to change that and how? Thanks!