Nice job on the unit. Like the red/black gradient there.
I think the transition between the flame is bit too sharp now, you might want to make some gradient to the base of the flame with the same green by using airbrush (if it can handle that kind of accuracy). Sort of the effect that is going on Eggroll's BAs power weapons and plasma guns etc.
http://www.dakkadakka.com/dakkaforum/posts/list/60/313003.page This would make the flames look like light sources and this way bit more in place
IMO.
I would keep the green hues on the flames gives nice sharp contrast to the reds.
On small note I would also fill the gap which is front of the barding below the neck of the horse. As it's on the front of the model it shows now bit much and can brake that nice gradient.
But looking good, waiting to see more of your
VC.
BTW, how do you like the new list? Haven't yet gotten chance to check it out myself.