Since 2017, Belle Regalia has had a monthly themed "Mystery Pack" which slowly developed into a box full of bookish goodies, known as the Belle Box.
Some of the past themes include:
A Tale of Wolves and Dragons
Kingdom of Ash (photo from The Booklover's Magazine)
The Grishaverse (photos by @thelattelibrary & @the_wonderful_reader_of_oz)
Christmas at the Bookshop (photos by @laurabookish)
Nevernight Mystery Pack (photos by @nikkireads, @fantasybooksrus & @laurabookish)
Sailor Moon Mystery Pack (photo by @nikkireads)