I’m going to suggest that doors are like furniture. They’re in the house, they are useful and functional and part of the decor! Here is a painted door that I decorated in my home 15 years ago. I had just met a beekeeper who I called the Honey Man (Alberto Ciampelli is now a good friend and recently we had a swarm of bees, which he removed, so I called him the Bee Whisperer – http://www.italiannotebook.com/local-interest/bee-whisperer/). I was so inspired by his bees I felt I had to have them in the house!
I painted the individual paintings on very thick mulberry paper and then attached them with water-based glue to the wooden doors. I then painted the wood around them (although now I realize that I don’t like the mustard yellow and so will repaint it blue at some point). Here is the detail of the bee painting.