For trains I find HS has the best pictures, but for some of the smaller things and details I usually check out Plaza Japan's site. One drawback: by the nature of eBay his pictures are only available as long as the item is in stock. These items are still in stock, however.
http://cgi.ebay.com/Billboard-Architecture-Facade-Assortment-Kato-23-470-/200394039660?pt=Model_RR_Trains&hash=item2ea86a616cPlaza Japan description:
"For use with Kato Billboard Architecture (Kato 20-470, 20-471, 20-472, 20-473)
*Not for use with Billboard Architecture Corner Shops (Kato 23-475, 23-476, 23-477, 23-478)
Facade Assortment comprises 4 kinds of different facades with windows. They can replace the facades originally installed on the buildings to enhance variety.
Billboard Architecture was built as shops in '20s and '30s and still can be seen in cities and towns mostly in the central part of Japan."
These strike me as the type of building found in places bypassed by modern prosperity. If these places weren't bypassed these buildings would have long ago been replaced by newer, larger structures.