I closed the question as off-topic, but not because of the constraint that holes could not be made in the wall. The reason the question is off topic is that it asks for product recommendations without relation to building or repair.
Although the question uses the words "make" and "create," I think it's clear that the user is not looking to build a shelf, but rather to buy something ready made. If he or she had described a challenge (e.g., described a particularly awkward space) and asked a specific question about how to design a structure that can support a shelf in that space or what kind of fasteners to use, then the question would have been on topic.
The root cause of this conflict is perhaps that the scope of the site is easy to misunderstand based on the site name. I suspect that to many (and especially to renters), “home improvement” means buying things at Home Depot that makes the home look nicer. In contrast, most of the regulars here are interested in the kinds of building and repair that homeowners do.