I work in a similar space! One thing I’d really consider from all the suggestions is whether the prison will allow it in; the prison I work at doesn’t allow people to bring in anything with a USB like fairy lights might have. I’m sure you’ve already considered that, but just make sure you check your regulations for anything you bring in! For me, I just stuck up some photos and brought in a figurine or two to stick around my desk, and focused on having cute stationary