This is the final draft of the email:
"Hello,
You should be aware of the fact that one of the sites you host contains design work directly stolen from a third party. The artwork in question consists of "Visual Styles", which change the appearance of the Windows XP interface. The person using your service to host his Visual Styles has several designs that have been lifted from the works of other digital artists.
For example:
http://www.peakpeak.com/~nicks/PreLuna.jpg
This is a v.s. called "PreLuna", which the author admits is "inspired" by this: https://www.wincustomize.com/library/accounts/Alexandrie/wb/prelunafinal.png, which is a "skin" (another way of customizing the Windows interface) designed and created by Johanne "Alexandrie" Cheine months before the v.s. of the same name was developed. The author of the v.s. asked Ms. Cheine for her permission to port the skin. She declined. This person decided to go ahead and steal her design anyway.
There are several more "rips" (slang for a copycat design) on this person's site.
I'm sure your company does not condone the presence of illegal artwork on your hosted sites, and I trust you will do the right thing and persuade this user against distributing materials that violate international copyright law, which is a prosecutable crime.
Thank you for your time,
Ricardo Colmenares"
I hope they do something... If hosting services crack down on rippers, we could all breathe a little easier.