I feel the Scare Floor Door System from Monsters Inc. would make for an excellent Fathead design. Fatheads are those large decals which are affixed to walls, usually depicting sports teams or pop culture items. You can head to the official Fathead site and check out their selection.
Basically you’d have two large Fatheads flanking the door, and a smaller Fathead on top of the door. A bunch of small flower Fatheads would then complete the look:
The problem is you’d need a door that has a central location, and is not near a corner wall, allowing for both flanking Fatheads. But the beauty of this design is that you could place the Fatheads on either side of the door.