I would ask for the suet, any decent marrow bones. There is very little chance of you getting brains, I would think. If you are feeling adventurous you can get the sweetbreads.
On the not raw side of things, I would ask for any knuckle bones, tail, tendons and feet to make bone broth with. Lots of good minerals and collagen there that go to waste.
Definitely get the marrow bones, even if they want additional money to cut and package them.
Oh, if you have a dog, you could try getting some green tripe for it(with the half digested grasses).