hedge made some nice castle stuff long ago for the first reina roja.
i'm sure i still have it somewhere.
as for other things, i have some stoneage themed buildings that might be handy that i made for zoric 9 (i think). since midevil themes generally use stone stuff they could probably be used.
heres some pics:
a simple building:
a cave-like house:
small kettle:
large kettle:
small quarry:
large quarry:
well:
worship stone
these next 2 buildings somewhat go together
Flintcar Wheel Fac
Flintcar Fac
the above 2 were used to make the Flintcar:

it has spinning wheels on it but i also have an unanimated version made if you want it instead. it just needs to be mapped so it can use the same texture as the animated version which is easy to do..
most of the buildings can be considered mid to very high poly for this game (especially the large quarry). all the bricks/logs used are full pieces copied and pasted to basicly 'build' the buildings instead of useing textured boxes so they all have alot of detail to them.