I designed this modular spray can holder system after failing to find something similar. All other options I've found either promoted laying the cans down (which is not awesome for the can) or were built for vertical stacking and took up quite a bit of space.

I therefore created a system for hanging cans that expands horizontally. The can is suspended only using a simple hook and no bottom. This works well by simply putting a rubber band around the neck of the can. The system in the picture has been working for me for several weeks and has yet to drop a can.

The system is modular in two ways:

1. You can expand the number of cans you can hang on the mounts by printing interlockers and additional mounts and just sticking these together and screw them to the wall,
2. The hooks are printed separately and slide into the wall mount which means you can design other accessories and attach to the wall mounts as well.

I've published two different kinds of hooks - one for a standard 400 ml can ("Spray can collar.stl") and one for the type of hair spray I use for adhesion on my printer bed which is a smaller 300ml can ("Hair Spray can collar.stl").