Music stores do it without problems. Martin Guitars sell leather hangers that attach to the tuning machines to facilitate hanging. Many companies sell products designed to hang instruments on the walls. That's good enough for me.

I've been hanging instruments with homemade hangers forever. Everything from fairly heavy solidbody basses to feather light ukuleles. There are no good physical reasons not to.

But there are some qualifiers. Do not hang instruments over radiating heat, or air conditioning. Drying or condensating conditions aren't good for the instruments. Uninsulated exterior walls can cause a sort of mini climate behind the hung instrument which may cause condensation, or expansion/contraction conditions to avoid.

However, I've hung scores of instruments without trouble, including the 11 in my studio now. My hangers are made of a backing plate of whatever hardwood I have at hand, usually either maple or cherry, and a pair of dowels set at the appropriate distance apart, mortised into the backing plate. The dowels are wrapped with leather, except in one case where insulating pipe wrap pads the headstock. Mine are high enough to avoid small children and pets, attached through the drywall (or plaster and lath) and into the stud with a 3.5" deck screw. (One hole through the drywall shouldn't piss off your landlord and is easily fixed when you leave.) Gravity keeps the instrument on the hanger.

Peace, Mooh.