One basic approach to selling on Zazzle, is simply to put a drawing or other work on as many products as possible. That way, the effort of producing a design is maximized in terms of the number of items added to one’s store, and, hence, to the Zazzle market place at large. Not everyone does this (for instance, some Zazzlers specialize in one product type only), but many do, including, usually, myself. And when a given design truly works fine on many different product types, it is not simply about adding more items at once; it is about offering people what one hopes are all good and worthy products.
Sometimes though, certain products in particular inspire a design, leading to “product inspired” designing in contrast to the “design first” way. This can be just one product in particular, and in fact, I have a “Few of a Kinds” category collection in my store for this very reason (well, more precisely, because I want to occasionally design for very specific items). Other times, this can rather be a subset of products, because the underlying inspiration, perhaps, is an intended use or purpose, one for which only certain products apply.

“Moonlit Dreams”
© 2015 Darren Olsen
It was for such a “purpose / product inspiration” that I drew, for instance, “Moonlit Dreams”. I was thinking of something to go on a nightlight in particular, and as nightlights are often useful to kids and babies, I decided on something suitable for a nursery. From there though, with a design so “baby” in nature, I soon saw how nice “Moonlit Dreams” could be on certain other products suited to nurseries, or, even, to some suitable for baby showers as well.