marc steene,
If your model could be mistaken for a highly recognized copyrighted character, you're probably in for some problems.
Basing your original model off of something established is fine as long as you have made enough changes so that it looks unique.
Here's an extremely exagerated example: I base a new model on Spiderman. My model better not resemble Spiderman in texture or physicality when I'm done. If anyone can look at my model and say, "Hey, that's Spiderman.", I've got problems.
I've seen your work so far. I like what you're doing. I can't wait to see what you come up with, in the way of a character.
Thanks,
Seth Black
Widow 13 - ©2008 Harsh Games, Inc