Primarily, library receipts!

I keep bookmarks whenever I get them, also picture postcards etc. I have some that I’ve bought, others I’ve made (e.g. knitted or embroidered). Mainly I use strips of thin white card that I razor off an A4 sheet.

Kleenex, usually since I can never find my real bookmark. I seem to have left it in a book somewhere in my bookshelf…

A sticker of cute dogs in space suits and the caption “we want fully automated intergalactic luxury gay space communism” because it reminds me of Ian M. Banks - also gets a laugh out of people 😁

My wife bought a few sets of bookmarks off aliexpress. They look really good. Here’s an example:

Here’s the link: https://www.aliexpress.com/item/1005004921501847.html, but you can find tons of styles and models.