Good news: For ambitious, creative couples with a very specific aesthetic in mind, an undecorated, open space—whether it's a converted warehouse, a photography studio, or a barn—allows you to have exactly what you want, from décor to vendors. You'll be hiring an off-premise caterer, which means that not only will you be able to customize the menu to your heart's desire, you'll also likely be able to save money on the bar—no liquor license means you can supply your own, and negotiate to return unused bottles. Because these types of venues tend to be located off the beaten path, you can play your music as loud as you want with little or no complaint.
Bad news: Raw spaces are, by definition, a blank slate, so there's no getting around the cost of rentals and lighting to make the space your own. You may also be looking at logistical difficulties: Does the space have an adequate kitchen? Is it weatherproof? Are there enough bathrooms? Does it have working heating or AC? Will guests have to use overtaxed freight elevators? And with remote locations and nondescript buildings, you'll have to be extra vigilant about making sure guests know where they're going (hire a valet service or station a point person at the entrance).