The Mount Si Motel, located at 43200 SE North Bend Way was transformed into the Blue Diamond Motel for Twin Peaks: Fire Walk With Me. It's located very near the Double R Diner and many other filming locations in the Snoqualmie Valley. Nothing about the exterior of the motel was changed for the film except for the sign. They did, however, add a wall in the room where Laura and Ronette are on the bed. Not sure why they did this as the new wall is only about two feet closer to the bed. The art department painted all the walls inside this room to give them a more "distressed" look. The gracious owner of the motel, Marlo, has kept the paint job intact for the last 20 years. All the work done on this little room gives me the idea that there was a good deal more filmed in there than we see in the final movie.
The crew also designed and added a big, red-neon diamond (not blue, as you might expect) to place atop the existing motel sign. The addition also served to cover up the words "Mt. Si."
While photographing the garage that Theresa and Leland stand in front of, I noticed a bicycle hanging from the back wall and thought it looked familiar. I checked my screen captures from the movie and sure enough, it was the very same bike seen in the film! I asked the owner's daughter, Sonya (who was giving me a tour and is awesome) and she confirmed that it was the same bike.