Brilliant painting. You really captured the resolve of a Draenei PvP player, paladin or otherwise. For the lore-junky naysayers here, take a look at the actual in-game model <Vicious War Steed>, before you criticize the content. SiaKim nailed it.
Paladins, in the case of humans, were created with killing the darkness in mind. Mostly first generation Death Knights, but a mass of orcs as well. So, paladins are allowed to hate, regardless if the Holy Light 'loves all.'
Draenei aren't in the Silver Hand. They're in their entirely own orders. As Vindicators, they can take heads. I'd figure this one is a Vindicator who is making an example of those who cross the Alliance.