Kallistra do Dark age buildings which work well for fantasy barbarian's as well as dark age you can find other buildings by looking at n Gage model railway stuff also I think 144th but not to sure on that
One of the schools of thought is that you should use smaller buildings with your figures, so with 10/12mm a lot of people use 6mm buildings so it looks better as built up areas ( I use this method). If you want to try this then have a look at Leven miniatures
I'm often asked what scale are the buildings used in the photos and videos with our 12mm/1:144 scale minis. Although we have started to make our own 12mm buildings, the older models in my collection tend to be either British 'N' scale(1:148) or older15mm resin examples. These days our 12mm ranges tend to more in scale with these older 15mm buildings than modern '15mm' figure ranges many of which now measure more towards 20mm.