My bedroom is in major need of a respray, but until I get around to arranging that, I have added some rice mods.
I recently replaced my car's front speakers, and as a joke I decided to try conneting the old ones to my home amp. I found that to my surprise, I got the best sound when conneting the front and rear speakers to the same terminals (it's a squeeze, but the cables fit) rather than using Dolby Pro Logic mode.
Anyway, the result looks like crap, but the sound is quite reasonable. I find that even ordinary rear speakers add tremendous depth to the sound. Most recently, I have installed a Dominator speaker grille.
Other mods I have considered include colour coding my room's door handle - though I found that I cannot justify mods like electric windows, tinted or double glazed glass or anything else too fancy. I'd rather save to move out!