As JudasIscariot said most of us just do covers for the GOG catalog. Here is a copy of a Gothic 3 cover that I did for a friend. . . your luck was with you. The quality is not very good on the back cover since the back image is hard to find and usually of poor quality. It is a cover though, I don't have a Gothic Universe.
It is hard to find time to make GOG covers so making random covers would overwhelm us very quickly. Thiev would have to make another catagory as well.
Hope this one will help you with your collection, you should open a GOG account . . .=)
Edit : Collectors Edition