Hey, Sweet Knight tribal deck! The deck seems really solid and very able to beat down hard and fast. I imagine the hardest pre-sideboard matchups will be against combo decks, but I doubt there's much that can be done to sure those up in knight tribal.
You seems to have all the best knights, and the only ones I can think of that might be good here are
Kinsbaile Cavalier (as a 1 of top end),
Accorder Paladin (to get extra damage through), and
Leonin Skyhunter (just to have some evasive threats).
As for the sideboard,
Leyline of Sanctity seems strictly better than
Ivory Mask (though it makes perfect sense if it's a budget consideration). Having some graveyard hate in your board would probably helpa lot too, something like
Rest in Peace or
Relic of Progenitus. They're good against Dredge (still floating around), any deck with
Snapcaster Mage, and any deck with Tarmagoyf.
Hope this gives you some ideas. Good luck!