D
Demon
Guest
It's all up to you at this point. Personally, I don't think your mana curve is too intense, 24 cards in the 1/2 slots, 13 more in 3, and 2 in 4. So I wouldn't put in another land, but that's just me. 
It all depends on how you wanna go with that last slot, if you want more burn/removal, you could use one of: Shower of Coals, or Violent Eruption, or Volley of Boulders, as higher end support for Volcanic Spray.
Another possible route, seeing as you're using 10 flashback cards, 4 of which have high flashback costs, is to throw in a copy of Catalyst Stone. Only costs two, helps you and hurts your opponent, and can be pitched if necessary, without too much regret.
I don't really know, it's totally up to you and how you want to play the deck, y'know more aggressive early or wait until mid/late game.
Sorry I couldn't be of more help, I'm tapped out on ideas
It all depends on how you wanna go with that last slot, if you want more burn/removal, you could use one of: Shower of Coals, or Violent Eruption, or Volley of Boulders, as higher end support for Volcanic Spray.
I admit that Volley is pretty darn expensive, flashback cost is too, so of course it would only be late game. For one slot only though, might be handy.
Another possible route, seeing as you're using 10 flashback cards, 4 of which have high flashback costs, is to throw in a copy of Catalyst Stone. Only costs two, helps you and hurts your opponent, and can be pitched if necessary, without too much regret.
I don't really know, it's totally up to you and how you want to play the deck, y'know more aggressive early or wait until mid/late game.
Sorry I couldn't be of more help, I'm tapped out on ideas