Recently I've gotten more into medieval-fantasy-esque style. I have customized my computer accordingly! I added a neat
font to my browser (firefox) and changed the settings so that
all text on the internet looks this way! It made surfing the web feel more whimsical, haha. I also added it to Windows, it doesn't show up in a lot of places sadly, but it's there!
I added custom cusors using
this great resource!! On my desktop, my cursors are mushrooms, and on my laptop it's swords, armour, potions. I used the 'Icons' tab of the same website to customise the icons on my desktop to things like shields, key rings, chess pieces, playing cards... My lock screen is a castle and the home screen is its courtyard with a cozy lit fire :D I don't know any programs, but just these couple options can do a lot for the look and feel of your computer!