Alas, it is not possible to visit the Imperial Hotel since it was demolished in 1968. Frank Lloyd Wright was an admirer and collector of Japanese art, so it is especially a shame that his most significant work in Japan no longer exists. Although the text is Japanese, you can see a photograph (#67) of the reconstructed entrance to the Imperial Hotel at the Meiji-mura Museum web site. According to Storrer the lobby was reconstructed as well.
I was surprised to see one of the stone urns from the Imperial Hotel on a visit to the Metropolitan Museum in New York. The piece was very pitted, possibly because it was made from Oya stone, the soft lava block used in the construction of the hotel. This photograph of the urn was taken with a low-end digital camera. No flash is allowed in the Metropolitan Museum.
The bookstore at Taliesin East has a couple of posters of the Imperial Hotel for sale. I have one framed and hanging in my office with a Cherokee red frame.
It must have been a magnificent building in its day. The book Frank Lloyd Wright's Imperial Hotel has many black-and-white photographs and some interesting commentary.
Drawing of Imperial Hotel (poster)
The official Fallingwater website has pillows designed for the Imperial Hotel for sale in the Museum Shop.