How About Orange posted a tutorial on how to make a simple wall decoration using just office supplies.
Make cork-covered vases for your desk. You could even use fabric or something other than cork if you don’t have any on hand.
Wall art that’s also a dry erase board by Paperstitch.
This last one isn’t really office-related but I thought it was very cute. Instructions on how to make citrus coasters by Curbly.