I agree with plants. Definitely at least some succulents. You can leave a cactus in the bathroom and never water it because it'll absorb moisture from steam.

Warm coloured lamps, adjustable, or non adjustable but placed so your lighting can always match the mood.

Nice pair of speakers, if that's your thing.

Disagree with what people are saying about art. Yes, get some art, but don't rush it. Buy what really appeals to you. Don't just get random shit for the sake of filling your walls.

Manual food processor. Chops and onion (or anything else) in 2 seconds. Doesn't need to be plugged in. Costs 10 quid. Cleans out as easily as cleaning a bowl.

Couple fridge magnets?

The entire works of Lenin. No but seriously, a nice wooden bookshelf with a nicely assorted set of books.

General bric a brac. I now buy really tacky mini sculptures of British Wildlife whenever I see them in charity shops, and I put them all over the house.

Homemade stuff, if you like crafts. I made a funny weed box, where it looks like Agent Cooper from twin peaks is handing you a blunt.