If you self publish you can put your book covers on products as well. You can direct fans of your books where they can buy these items.
Smaller low cost items such postcards, photo cards can go into media kits.
Mugs, and bags, and cell phone covers can be door prizes for events.
Some Zazzle artists are willing to do custom jobs as well. They will still own rights to their art but can create products that only you can buy to promote your items.
Samples of my products for writers
I write Books 12290 Mug by AbundanceLoveTrip
Design unique personalized mugs for kids online at zazzle.com
Zazzlers who want to be promoted
Zazzle adds easy art to your blog that can complement your writing. If you're a fantasy writer, you can add some lovely products of amazing fantasy artists giving a distinct look to your blog. Now, if you write literature, there are many products from photographers and fine artists. If you write non-fiction articles on eco-friendly products, you can use the referral plans to highlight eco-friendly products. This will save time. You won't have to hunt pictures down on the web and asking permission for each item. It will help you promote your writing while at the same time save you time so you can devote your time to writing.
I will not know who refers your stores if any. Make sure your shop looks your best