How do you mind the gap in your shelves?
I obviously like to have plenty of room available for the collection to grow, but for display aesthetics, I also don't necessarily love having giant gaps in the shelves waiting for books to fill them. I turn some of my books cover out to fill the space and feature some of the artwork, but some spaces work better than others. I utilize action figures sometimes as well, but I don't like mixing them too much because I consider the shelves with books as an "active library" if I want to pull one down to read, so I don't like having to shuffle figures out of the way to be able to grab a book. So generally the figures get their own space, and the books their own as well.
Image is a bit of a work in progress trying to figure out the shelf display behind my desk. Do y'all have any shelf hacks you use to utilize the space while waiting for books to arrive?