The digital art thing is big in hospitals (Source: I was the technology designer for SFGH, UCSF, and the technology implementation manager for El Camino Hospital - and director of OPs for Vizio (TV))
Ive evaluated, purchased and installed systems such as this, and wayfinding in hospitals - paying hundreds of thousands for digital artwork to be looped in elevator lobbies, room screens etc - they, like you said - had rubbish software.
For the lobbies in El Camino Hospital, I had to replace some units with Mac Mini's playing an MP$ on loop via VLC because the digital signage system was so crappy.
So, having this with a piZero would be great.
However - wayfinding would also be elegant with this - so long as when you say "interactive" surely it could display a webapp/app via the PI, and "screen-saver" to your digital art loop when idle...
But - seriously, the digital art/signage/wayfinding market needs a fiesty upstart like you to ruffle their muffins - I dont have any PIs currently else, I'd be using this....
I wonder if I could install it on my shitty android TCL tablet from T-Mobile...?
(Also look at controlling Feit Electric bulbs)
EDIT:
I think the most lucrative option for a device/OS like this would be travel signage at BART, any 'regional transit' -- find the dumbest person at that organization and train them to install and configure and display something in a fool-proof manner...
Look at Sacramento (california) regional transit - they have so many screens with zero usable information...
Have you been in a train in APAC? THey have LCD screens with status maps on the upper walls...
Have you been in a train in the US? THey have pee and poo on the upper walls, and zero map status anyplace.