Hmm..... *DEEP BREATH*
Arcade/pinball machines, bean bag chairs, mats that aren't round (can't count the number of times I wanted a mat that didn't leave blank spots...), beds, working T.V.s, more plants, dolls, etc., a mannequin with changable clothing, a computer, lighting such as lamps, customizable things such as posters that you make with something similar to the firered/leafgreen picture-taker so you can have a 6 spaces long poster of all your party pokemon, a spa or mini-hotspring, non-poster wall decorations, such as wallpaper, vines, or shelves, sound-test-style music player in various styles such as phonograph/oldstyle radio/CD player, an umbrella, japanese-style ricepaper walls to segregate the room, dolls you can stack with each other to make piles of them, fish tanks, bookshelves, a rotatable globe depicting the various regions of the pokemon world, statues, paintings, scenery from other parts of the game (equipment from a team -whatever they are this time- base, pokecenter decorations, miniatures of landmarks, etc.), diaramas, fake windows, mirrors, stairs that go nowhere (or better yet, 2-story bases), ice cream makers and churro machines (yum), playground equipment, gym equipment, larger and detailed depictions of your watch-thingie's functions (like a clock), couches, drawers, fountains, kitchen stuff, mock-video game equipment (like is in your room in like every pokemon game), replicas of famous people (the professors, various gym leaders, whoever else shows up this time around), a giant pokeball that captures you for a moment as an animation, holes in the floor that you jump over when you run over them, a birdcage, theme modifications to change the walls and floor entirely, an elevated section of floor that you can continue to put things on, a giant fake nintendo DS that plays random demo battles, easy access to things like your WiFi battle record, PC storage, etc. etc., trophies, stands for said trophies, multiple shapes and sizes for the same style of desk, paint to re-color existing items, making a red pocchama doll or something (hope I got that name right), a trampoline, the keyboard mats linked together into a single item, items to alter your appearance temporarily (like a bomb that explodes and leaves your character all black, or a bit of water that leaves them wet, or whatever), sleeping bags, ways to display your achievements to visiting trainers (like trophies but....better), repeats of every item offered in ruby/sapphire via whatever link-up you use to get your old pokemon into D/P, the ability to display normal items as decorations, such as a water stone or a potion, and just...MORE of whatever is already out there, just more of it!
*GASP* Catching breath, catching breath.......okay, whew!
Well, there's gotta be a few good ideas in there! ^_^