There's definitely some wonderful fan sculpts out there. There's no consistent quality since they come from a variety of sculptors but there are certainly some very nice ones that look great and are clearly sculpted at 40
mm scale that fits MCP just fine. Characters without rules can be tricky, but if you find a character that you can proxy as (I'd recommend Ulik) it should work fine.
Here's a shot of game vs one of my friends that printed a set of Web Warrior proxies.