There was a period of time where I couldn't assemble/paint buildings and structures fast enough, I used to sell raftloads of kits I'd build and paint as well as custom painted scenery from Hobby Bunker, TSSD, CTS, Formtech and others.
The bottom fell out of the market for me about five years ago; numerous customers told me space had become an issue, so they stopped buying buildings and other scenic items from me, that was around the time I dropped BAR due to lack of sales.
I used to have numerous custom painted items for sale at the shows that were parts of my displays, I cut way back on them again due to lack of sales.
I have noticed in the past year or so a bump in sales of painted buildings and scenery for me at shows and on Ebay, so maybe we've got a new batch of collectors interested in these sorts of items.
I came into a number of Conte buildings back in July and they were basically all gone by the time Chicago rolled around, the remaining ones sold there.
The one to talk to on this is Matt at HB as he produces the widest range of buildings and scenery, he'd have a better handle on what does and does not sell/what the demand is now for scenery.
I recall several years ago someone from the UK contacting me about carrying a range of buildings he was working on, including a complete La Haye Saint as well as other larger WWII type battle damaged buildings, but it died on the vines and never got off the ground.
As with anything, the demand from people is what drives the supply.