I know there are blind panels available to cover the empty space of your modular and to protect it against external factors. Now I was thinking of the following:
Having some kind of panel that makes use of the depth of your modular. It would look like some kind of “U” shape and enables you to store (small and handy or decorative) stuff in it. The unit in fact becomes a tiny closet. You could store short patchcables in it, laminated cards with references to modules, the small passive multiples or even just a nice artifact. Perhaps there is even room to create a (horizontal) row for a passive multiple.
Maybe it’s not interesting/worthwhile (or it already exist) but would just like to share the basic idea. Also created a mock-up to illustrate the idea based upon a 16HP module. The sides of the module should be covered too.