Wrinkles in Legendary backseat back...**PICS**
I've seen a lot of cars on ebay with "new seat covers" stated in the description and wrinkles shown in their pictures so it is somewhat common.
If there's enough filler in there the skin will fit tight. It's supposed take some real labor to get the skin on. I had my son ( 180 lbs ) standing on a piece of 2X8 spaning the frame and compreesing the assembly while I hog ringed the skins on. No wrinkles. Experienced professional installers should know these things.