If you are good at sewing, you could open a blanket repair business - many people have horses that destroy blankets, but those blankets are expensive enough to want to get repaired. This could be profitable.
You want to be unique, but there is no reason why you couldn't make horsehair jewelry your own.
Going off of the horsehair trend, you could decorate custom frames with a clients horsehair to make a frame to feature whatever horse that hair came from.
If you are really ambitious and want to really work at getting GREAT at sewing, you could begin to make show clothes or even themed renaissance apparel... there is a market for native costumes for Arabian horses if you are in a region of the world that has a big Arabian show community.
Possibilities are endless!
Toofine - 1998 Half Arabian
Minnie - 2013 Morgan