Question

what is missing from this free body diagram of a sled being pulled across level ice by a dog team

Answer 1

The normal force
the force that the dogs exert on the ground because of the weight
the velocity vector arrow for the sled
the reaction force that the ground exerts on the dogs to push them forward

Answer 2

@ganeshie8

Answer 3

The FBD must show all the forces acting on the "sled".

I think the normal force is a must.
Forces on other objects like dogs are irrelevant in the FBD of a sled.