What's the best way to save assets for hanging on walls like LCD screens, pictures etc

I’m creating an asset library at the moment and was wondering about what orientation to save asset that will be hung on screens?
should they be orientated as they would be hung so say the front of a picture along the y axis or does the front of the picture need to be orientated along the z axis so if flat to the ground plane, then it snap correctly to a wall object.
Not at my main computer at the moment so can’t test this out.
Any help would be great