Here's how I'm looking at it. Bear in mind that I'm a clueless newbie. It's in the covenant that we can decorate the inside of our house any way at all that we like; only the outside needs to conform to a general theme.
So who's to say that my avatar isn't fresh out of college and poor? She inherited a refurbished Victorian in an old neighborhood, from her great-aunt. She moves in with her collegiate orange crate furniture and bean bag chairs. It's her house and her style, and she's not only not hurting anybody, maybe she's a breath of fresh air in the neighborhood. Maybe she bikes around the neighborhood waving to the neighbors, and the stodgy old blue-hairs think she's cute as a button. Maybe as she earns more money and gets a bit better taste, she will begin buying nicer furniture, but it will still be in whatever style she chooses.
That's my RP way of justifying a mish-mash of styles. For those who are now thinking, "but I don't roleplay", I contend that everybody who is even considering buying period furniture to match the style of their house is roleplaying right now.
I'm enjoying the challenge of finding low cost, low prim (hopefully both) furnishings that, in my mind, can loosely fit into a Victorian theme. I've got some Queen Anne-ish, some Chesterfield-ish, side by side with a few distinctly modern things like picture frames and a steam punk clock. It all looks good to me. It's all pretty low detail and cheap, but it's a work in progress. I've got a porch swing that I love that I think looks distinctly American midwest or maybe Cape Cod-ish. It looks great with the house, no matter what period it's from. I also have a tie-dyed hippie flag flying from my cupola. VERY unusual for this neighborhood, but I dig it and it helps me find my house! LOL.