Great potential. Liked almost everything about it (graphics too). The battle system needs you know, a little something to make it stand out but if it was multiplayer, with you able to select from a wider range of opponents.
Don't know if you need any but I thought of a couple of ideas.

Necromancer - very weak and useless except for one redeeming feature- he can raise dead characters (with very little energy, and not always successfully).
Barbarian - About as tough as two knights but only able to move one step at a time. Low resistance to magic. For extra coolness you could do a barbarian astride a tiger or some mythical beast.
Chameleon - morphs to whatever character he approaches/is attacked by for one round. So you have at least a fair fight.