Horses and Ponies from the Celtic Regions: The Manx Pony

The Manx Pony is an extinct breed from the Isle of Man, but should still be covered since it is descended from the Celtic Horse. Thankfully, they survived long enough to be photographed. Skeletal remains have also been discovered on the island from the time of the Vikings. However, the tack buried with the horse was Celtic in origin. They were used primarily for heavy work; such as: pulling, hauling, plowing, and packing. The last pony died in the late 1800's.
The average size was estimated out to be 13hh. The color was unknown, until an agricultualist named Thomas Quayle documented that their colors were Bay, Black, and Grey. Dark Chestnut has also been documented. 

Resources:
http://asmanxasthehills.com/the-manx-pony-native-isle-of-man-celtic-extinct/