I've been in nursing almost 30 years, as a generalist and, now, many years as a child psych CNS, and I've never seen any real possibility of incorporating art background/expertise into nursing as a professional advantage (other than being the person who does the arty reaction groups on psych units, which is usually done by techs, not RNs.
You may actually want to look further into art therapy. Since they are used quite a bit in psych settings, I've known a number of great art therapists over the years, and they have all loved
what they do (they were much happier about being art therapists than most of the nurses I've known have been happy about being nurses ...). You're right that few facilities use an art therapist enough to have a full-time position, but some of the people I've known have worked at a number of different facilities as a free-lance contractor, and really enjoyed that flexibility. Also, larger facilities, like state hospitals, schools
for "special needs" kids, and larger psych facilities, do
have full-time staffs of art therapists.