I've been looking for a replacement pair of tall brown boots ever since mine had a bit of a wardrobe malfunction a few years ago...
These Studded Frye Boots are quite cute, but way too expensive. The Steve Madded Feud boots are interesting, but I'm not completely sold on the tie up the back.
J. Crew has a very nice selection of boots. I have a fairly large calf for my body size, so J. Crew is good source since they make most of their boots in both regular and with an extended calf. I think the pair on the left (Tenley High Heeled Boot) are my favorites, but the kitten heel (Rivington Boots) might be slightly more practical.
Two pairs with an even lower heel and more equestrian look are the Tenley Low Heeled boot
and the Richmond Boot.