As far as reputable Merge Skins, check the Internet Poker forum here on 2p2. Carbon and RPM sponsor their own sub forum, and other skins have their own support threads there. It is pretty easy for you to make an educated decision. Most, if not all Merge skins seem to be on a central cashier, so you're looking at promos and customer service as your primary variables in this decision. Good luck.
Would you be upset if I stole certain parts of this =P