Picking through a crate of reclaimed floor tiles, Micheal Ghyoot pulls out a model with a blue, gray and white art nouveau motif. "These are easy to like, because they have this floral pattern," said Ghyoot, a researcher specializing in architectural  reuse, holding up the square cement tile once common in many homes built in Belgium in the early 20th century. "And, in the '30s and '40s, they started producing more modern patterns, and these are super interesting as well." The crate is just one of dozens containing tiles of varying styles, sizes and colors, all waiting to be cleaned and sorted for resale at Rotor DC , a Brussels-based cooperative specialized in salvaged building materials.…