I had this old, disgusting fold-up chair as my desk chair at my parents' house for years. Finally I got sick of it and improved it.

For the seat cover, I got one of those scrap fabric packs they have at Micheal's for about $4. I patchworked it together VERY roughly- I chose wild-patterned fabric on purpose because I am a horrible sewer.

I unscrewed the seat and the back from the chair frame and painted that separately. Then I measured, cut out, and staple-gunned the fabric to the pieces that I unscrewed. I also added a new piece of foam rubber to the seat. Then I screwed the pieces back in once the chair was dry, and voila!