I love the horse barding. The purple is nice and the castles are beautiful. Personally I'd skip the black or just use it for the underside of the fabric. It's lost on the outside (and heraldically improper).
You'll do better if you brighten up the metalic golds because they look more bronze and don't match the superbely done painted castles.
I likethe way the purple and greys tie in with the yellow.You definitely know the feel of the Bretonians. And you're cool enough to name your work. Thanx.