No, people needn't worry.
Even if characters aren't my personal favourites, I know how distressing it would have been if I couldn't mesh or skin and someone who could said "I won't be making your favourite characters".
I'm not going to do that to people.
The only difference is that people will have to request Xmen, Ultimates New Avengers rather than me just making them off my own bat.
And provided that people are reasonably polite, (and don't justdemand stuff), and assuming I'm not swamped with requests, I pride myself on not turning requests down.
Again, I try put myself in the position of the requester, and imagine how it would feel to see others get their favourites made, only to have mine turned down. I'm not going to do that to people.