Any suggestions for my Magic the Gathering Standard Knight Deck?

If it were me, I'd put Accorder Paladin main deck and Skyhunter sideboard. You are definitely aggro so you may gain a lot from the 1 extra power and Battle Cry. Another suggestion is adding Contested War Zone instead of Sejiri Steppes. Like was already said, Sejiri Steppe has too much downside whereas war zone can be brutal with your creature heavy deck. All in all i really like it and have been considering the same sort of deck once i get my hands on a few more Knight Exemplars. I think the biggest challenge will be against Black with Grasp of Darkness and Black Sun Zenith so bekeep those White Knights in the SB!