I’d do wallpaper. At least when I got a quote to paint our small office, including windows and trim, it was high -1200 bucks- because the office could only accomodate one painter and it would take him all day. I think a small room is perfect for wallpaper. Choose the rug after wallpaper.

I have a small home office (9x12' finished former sleeping porch) that I would like to look nicer. Have you done something that was particularly high impact?

I'm thinking curtains, rug, and paint that go for an old school library/ study vibe. Maybe bookshelves (something that would look nice but isn't super pricey?) and/or wallpaper (is that ridiculously expensive to install?).