If I give a nickname (and I do it a lot!), I usually just shorten up the name. For example, my boy's name is Snickers, but I mostly call him just Snicks. On other occasions, I may nickname a horse after a distinct behavioral pattern or after the looks of the horse, for example, Snicks sometimes becomes "Mr.Moose", if he acts up, as his face once reminded me the muzzle of a moose, or Trickster, when he's particularly playful; or a filly, named Fiona, sometimes becomes "Finx", just because I like the sound of it. Be creative! :)
Aerial doesn't seem girly to me at all! I guess I'd nickname Ray or Aires.
I have come a long way, to surrender my shadow to the shadow of my horse.