@newgardener, It's quite a shame that the AC was placed so low on the wall, it would be so hard to sit under it when on, you would get a stiff neck from the cold in no time. It should have been right up below the cornice, then artwork would be simple. If it were me, I'd have it moved up, repair the move and you have your wall back, not particularly an expensive job just a bit messy.

None of them – too busy, too contrived and really the 'art' feels dismissed and unimportant (and I suspect that that is probably the case – if it were important to you because of beauty or sentiment or genuine interest it wouldn't be relegated to an over-busy wall just to complete some grid or slightly random pattern). I have a lot of paintings, drawings, etchings and photographs around my house but each one is there because it has meaning and adds to my life and aesthetic pleasure. When they have to share a wall I spend time ensuring that each is still able to be seen, appreciated and respected in its own right.

Zazzle.com.au have some cool and affordable posters you can then frame with IKEA / KMart / target frames etc... try searching graffiti for something edgy or beach photography for some Cali type images... or there's architecture shots too. There's multiple sizes available and you can then try matching up to frame before purchasing.. Good luck

Because the bedhead is curved, I am not sure that rectangular art will look great...maybe try something a bit different ?