If you're such a Marvin the Martian fan, then you should know that his name is not Marvin the Martian. In the actual cartoons, he never had a name - it was invented by marketing people years later when they started making t-shirts and all that crap.
Anyway, why didn't you use the search feature at classic.winamp.com ?
There are already two skins there:
If those aren't good enough, you can easily create one of your own - it only takes five minutes or so - by whacking your favourite martian picture into one of these programs: