A shoe would be covered in Velcro or other suitable material and the customer would buy a kit of patches to cover his/hers shoe - to customize it so to speak so s/he would be able to get lots of combinations. I realize this would be a fad appealing mostly to kids but perhaps it would be worth looking into it.
I am no graphic designer to illustrate this concept, but some time ago I found a few web pages which give an idea about it:
For an art project children painted the shoes. Of course the shoes were spoiled so why not achieve almost the same result by using a Velcro shoe + kits.
Also, there is a Chinese company that already produces shoes that can have
different images attached,
so something similar to my idea but not to the extent I envision (i.e. fully 'customizable' shoe).
Perhaps my idea is not so far-fetched as Ralph Lauren was selling at some point 'Paint Your Own Polo' kits .
This is an ad for a charity run: