This is a simple mount system, composed of 2 pieces, one “Object.stl” goes on the object that you want to mount on the wall, the other “wall.stl” goes on the place that you want the object to be.

The “Spacer.stl” is to prevent the piece from being angled in relation to the wall.

This is for small and medium-sized objects, I didn't test it, but it can probably hold about 3 kg.