Reading papers while in display cases would be neat. Main use case I have in mind is for poetry or "historic documents" like treaties etc that would be nice to be able to display. 

Making that possible might also mean making it possible to read a letter on a counter without picking it up, which I think would be handy.

Possible magic school: Dreamwalking

Casting puts you to sleep. While sleeping from the spell, you can see the area around you. You can move around an area invisibly (your visible body remains asleep in place), area determined by level of cast. 

A second spell can allow you to manifest an image of yourself with a skill check almost like reverse-hiding (the better the check result, the easier you are to see or the longer it lasts). While manifested, you can talk with waking critters in the area who can see you (if you got a poor check result and they don't see you, then either they don't hear you or it comes out partially garbled).

You can freely see and converse with other dreamwalking critters in the area (secret dream cult meetings!). Maybe there's no language barrier in the dream?

You have no physical effect on the world while dreamwalking (can't attack, pick things up, open doors etc) and your dream form is similarly invulnerable. Maybe physical obstacles don't stop you (e.g. doors, trees, water etc)? Grey sigils create an impassable zone around them in the dream, so they can be used to ward rooms against eavesdropping.

Another spell could cause a named player to also fall asleep and either enter your dream, or you enter theirs. This would be subject to the same sort of consent/resistance as summon etc. If they're brought involuntarily into the dream, then there's some kind of way for them to struggle and leave it, perhaps either by fighting you in-dream, or maybe them clicking the "wake" button makes a check against your cast (on a short cooldown?), and the spell releases them if they succeed. Or, maybe their body is just protected while in-dream? That would enable a dreamwalker bandit to "capture" you, and their buddy could get into position while the dreamwalker explains you're being robbed etc, but you don't just get fleeced automatically as soon as you're asleep. This seems like a similar level of threat to hostile summoning.

Obviously not a fully-fleshed idea, but something that came to me and I figured I'd throw it out there.