I can't think of a pullup that is only plastic backed. However, I think a fair number of them likely have plastic underneath the cloth outer cover. Take for example goodnites, if you peel off the cloth cover, it will reveal the plastic cover underneath, which does have the designs on it.
I haven't seen or heard about any plastic-backed ones, but Ace is right. When you tear off the cloth cover on Goodnites, there is a plastic second cover, but it doesn't have the same feel as the original plastic-backed diapers.
well it really wouldn't make any sense for pull-ups to be plastic backed or plastic covere anywhere at all, because just like almost any other diaper, there not made for AB/DL's and pull-up's are made to be as similiar to wearing real underwear as possible. and besides companies like bambino who do make them for ab/dl people like us.