Hmm true, I missed that part o:
But Mick, I want to give you some suggestions.
Google is your good friend. I'm not familiar with the character but I found 2 pics in about 2 clicks.
Rather bad quality for the first and the second is a bit small, but as an artist you could work it out. But if you don't like those I believe there's better images out there, just hard to find.
Free renders are rather nice to work with but you need to learn how to make renders yourself if you don't want to always count on others and could still make great sigs.
I don't want to sound harsh, but I felt you didn't try hard enough to look for the picture the guy requested.
If you want to learn something, you can always google tutorials or ask others who are more experienced (I'd be willing to help too). I'm 100% self-taught with the use of making the effort to read tutorials, practice and learning from them. I think tutorials could be very useful to you as well.
Don't give up, and build up your confidence along the way. If people don't take your art seriously, show them you can make something magnificent.
/goes to make siggies