[Here is my first pony, Amanda. 12. Hands, 20+ years old. We think she was a Quarter horse/Shetland cross. This picture was from when she first came, she became a much better weight with regular riding.
Shorter limbs, flat and long arm, closed shoulder and elbow joints, blade slightly upright but has good extra length. The fore has scope for stride extension and appears as the strength of the topline.
The back may be a touch longer but can't complain, it is very well supported by a very deep girth.
The crop is certainly shorter, and if that hind leg was pulled under correctly I believe the upper hind bone structer would be shown as being significantly lean.
Nice height/length ratio and I suggest would throws to English once fit. Best on flat, probably dressage stuff suits best.