My new crazy guess.
A Bullmastiff mix!!! Yes I said it. This is from the creator of the rottie/jack russell mix. I really have no clue and I'm just having fun with this. The amazing thing about this dog is depending on what angle you see him at he can look like a completely different dog. Below is his "bullmastiff" pose picture, though it may just reinforce the rottie idea.
Alot people are saying Shepherd to explain the saddle, I really just dont see Shepherd in him. Alot of hounds and some terriers also have black saddles. And does he necessarily have to mixed with something with a black saddle to devolve the black hairs along the back?