If I remember correctly, he's a Percheron named Tristan, owned by a friend of Tobus's. I remember commenting about that photo as one of my first posts here on Xmarks. I have a love for Perches, so it's one of those facts that stick in my head.
Yup, that's right. He's a Percheron. I used to do a lot of work with Percherons, mainly pulling stagecoaches, carriages, wagons, and ploughs. I fell in love with the breed. They are truly 'gentle giants'.

Sadly, I don't own any Percherons myself. My horses are normal-sized breeds, mostly Paints. So if I'm riding, it's usually going to be on a Paint horse, wearing boots and jeans.