I'm a big fan of mixing up styles whenever possible— one of my favorite rooms has an oval midcentury dining table surrounded by French bistro chairs and an antique pie safe. Mixing it up sometimes works, and sometimes doesn't. It takes a certain flair for combining influences, and it takes awhile to get it right. It's all about experimenting.
That said, one thing I've found to be successful in any decor? Industrial elements used sparingly. Just a slight nod to the useful — say, in the form of a metal locker, a restaurant-grade gas range, a photographer's light, or a metal bookshelf — can bring a space together. An industrial element can downplay a super-saturated wall color, offer a sense of purpose to an otherwise frilly or ornate room, and add a dash of tough-as-nails-without-trying-too-hard to any space.
1) Painted metal shelving and a super cool metal pendant photographed by Magnus Anesund via Emmas Designblogg.
2) An amazing metal cabinet from Tara & Ryan's Swedish-Industrial-Ruralist Weekend Home.
3) A simple photographer's light, placed next to an ornate velvet setee in Abigail's Modern Condo.
4) Lockers are good storage and can be nice to look at, too! From Xing's Eclectic Bellevue Home
5) A stainless steel island beneath a Schoolhouse Electric light.
6) The perfect gas range completes Rebecca's 70s Drab to Industrial Chic Fab Kitchen.
7) More cool lockers, this time in the bathroom, from La Journal de la Maison via Desire to Inspire.
8) Heavy-duty storage in a Brooklyn home via Design*Sponge.
Images: as linked above