Originally Posted by frost

I already mentioned that I thought prem membership are the only ones that should come with avatars. I think that would encourage many people to become premium.
If you didn't feel comfortable going that far, you could give the nonprem members access to only a dozen or so canned avatars, and let prem members only make custom ones.

I don't think signature lines are enough to encourage people to join, but if it's one of several things benefits then it couldn't hurt.