If you're alright with it Stiggy, I'm sure someone could make a custom cover. There's enough hi-res art for Friday 13th and A Nightmare on Elmstreet on the net. You could have the Friday 13th game with a cover from let's say the poster art from The Final Chapter or a Nightmare cover with the poster art from Freddy's dead or something. If one were to go all wild on these covers you could have a custom spine with the Freddy vs. Jason art if the games stand next together on your shelf.
If you want the retail cover then it's like Shenske said. We'd need the scans with at least 300dpi (600dpi preferred) and derasterized/descreened.