Hola Alex!
Great to see that you havemade some more progress on this piece! I have a soft spot for Alexander the great as I have read quite a bit about his conquers.
I do have a couple of pointers on the horse, first of all it appears to be a tad big for the rider, now Buccephules (sp?) might have been a beast of a horse, if so, your fine. Although Alexander wasnt exactly a big guy either, so it may be just right.
The second thing I would suggest doing is make the neck a tad thinner at the 'throatlatch' where the neck and head meets, although this horse was a stallion, most of them have thick necks but they still taper some, if you would take off just a little not too much right under the head I think it would look a lot better.
It is great to see that you didnt sculpt a horse with human teeth, a funny error so many sculptors seam to do!
Keep it up and Im looking forward to see this piece finished!