Painting or wallpapering sounds like a nightmare to me, given my poor coordination and absent-mindedness. No doubt, most autistics with similar traits would feel the same. Tempaper is an interesting alternative. It’s as good as standard wallpaper, but has a self-adhesive backing and is repositionable. Most important of all, it’s removable and (on most walls) doesn’t leave a sticky residue. No glue to spill, no messy brushes and if you make a mistake, just take it off and try again.