Artist is HissatsuNeko; it was commissioned by a fan and the description on Hentai-Foundry is:
"Ridden by two little person tamers , two human pony sluts fight each other with their arms bound behind their back. The loser is punished by the crowd. The jockeys have forced the ponies to ram each other so they can fight up close with their little arms and painful toys. The ponies have to make contact or charge each other at least once every two minutes or be subject to anal tasing. Wins are by submission, knockout, or unseating the rival jockey.
The Loser is punish by tit hanging , massive buttplug hammered in with a paddle, or canes broken across her ass. All while being fucked by fans."