To be terribly frank, if you want a horse befitting a shadowknight, act like a shadowknight. Win epic battles in Lucan's name, master a craft, or generally pillage the land for the resources to acquire one. Freeport provides you with a lame mount for being a lame example of their dark crusader. Becoming the pinnacle of your class over a long journey of developing the character is when you earn the right to ride an impressive looking horse.
A plain black horse with red eyes is good enough for a mediocre shadowknight, if they want a fire spewing abyssal mount... well that just takes more work than pressing the SK icon at char creation and soloing owlbears.