I have a friend who plays/played a similar build, but with more Deadbridge Goliath and Tormented Souls. Aggro sorta just chews that deck apart though, since you force him on the defensive and just kill things before they get big enough to be a threat. I always had things like D-Sphere, O-Ring, and Selesnya Charm to deal with them. He'd play essence Harvest and I'd just exile his big thing. Made the guy really rage.
He then tried to play Angel of Glory's Rise Reanimator, the self-mill Human tribal-ish homebrew deck that shut down BR Zombie/Rakdos Aggro in a GP or STar City open at one point. And he neglected to realize that I wasn't playing BR Aggro, so it did nothing to me. And then I sideboarded in 2 Rest in Peace and it just shut him down completely.
So basically you have to find where Cockatrice stores its images on your computer. Mine is in c/users/my name/app data/local/Cockatrice/pics/downloaded.
What you do is rename the hellrider picture I sent you Hellrider.full and find the DKA folder with the original Hellrider.full. Then you just replace it with the new one. It might be easier to just open up a hard drive search for Hellrider.full, now that I think about it.