This is what I like most about the miniatures hobby: converting. It starts by selecting some bits and pieces from your bitsbox. I had a spare barded horse from Battle Masters and wanted to use it for a High Elf hero.
The legs are metal. The torso and head are High Elf bits.
The arms are from the Tiranoc Chariot sprue. They look fierce on this mounted hero model. The shoulders didn't fit perfectly. That's when my 40K bitsbox came in handy: a pair of (Tau) Kroot shoulderpads!
I tilted the horse backwards slightly to make the miniature more menacing. Tree bark and pebble chips were glued to the 50mm square base*. The horse received Elven feathers as head ornaments.
To make the miniature a true High Elf leader I added a sheated sword and quiver with bow and arrows to his saddle. I also tried to add a cape but it didn't look "correct".
* Why a 50mm square base you ask? Well, in Warmaster 28mm games a cavaly stand is 5cm wide, 5cm deep...