One of the first things you'll do with the HoloLens is place little holograms around your room, and it'll look like you have a large figurine collection. Ralph Barbagallo, Edward Dawson-Taylor, and their HoloHacks team decided to take that a bit further and created an app that allows the user to produce and tour virtual art exhibits.
You can see the concept app (tentatively titled A Day at the Museum) in action in their video above (you can also check out this video for another look). You simply place art on the walls where you want it, and then anyone in tour mode can look at the exhibit. It's a very simple concept but has several positive applications.
Aside from creating virtual art tours that people can take just about anywhere, if you actually ran a museum and wanted to design an exhibit, you could do it in the HoloLens before staging it in physical space. Integrate the features of Holo Voice Memo and you have an excellent tool for viewing and learning about art.