Really whenever you loot a first aid kit, defibrillator, fire extinguisher, exa, you can place them on the walls (maybe just add a single metal scrap?). And when you need to use them you can take them off, via normal interaction.
Also there can be special “placed” spawn nodes for these.
Go into a restraints kitchen, it may or may not be mounted on the wall to be looted, or to a watchtower you may find a intact medkit still hanging on the wall.
What if you could use a hammer and some nails to either put nails in walls to hand items from or pin items?
Also, I seriously think that almost every single item should be able to place on any flat, horizontal surface and could either be directly picked up or interacted with (like filling a magazine held in your hand with an ammo crate placed on the floor).