What type of mural would you paint on a door?

My home is pretty old (97 this year), and some of the proportions on the doors are very unusual. Replacing the exterior doors on this house would cost a small fortune, so I have no intentions of doing that any time soon. My front door has a bunch of windows in the front, and a very old doorknob with a simple lock. Since breaking in would be extraordinarily easy, we keep a large panel screwed onto the door, which covers all of the windows. It is flat and white, so from the outside you can’t see (or break) in, and from the inside it just looks like a white panel in the center of the door.
It isn’t exactly beautiful, but it’s not hideous, either. I used to keep a curtain over it, just so that it was a bit “prettier,” however, I recently redid the room that my front door leads to be my art room, and I would like to paint something on that panel ( visible from the inside). I have seen door murals before, and while I don’t think I would want them on the interior of my home, an art room with a quirky door seems like the perfect place to do it.

I’m just trying to brainstorm. I am totally open to getting creative with it, something unexpected, not necessarily the illusion of an outdoor scene (for example.) Suggestions, pics, etc are very welcome. Thanks! :)