Any thought to
Mimic Vat and
Mirror of the Forebears for doubling effects on
Scourge of Valkas as a damage outlet. Or even
Warstorm Surge and/or
Where Ancients Tread to make every dragon's token go the extra mile.
I'm also with the thought of more ramp/mana reductions like:
Urza's Incubator, Extra Planar Lens,
Caged Sun, or
Gauntlet of Power. Even
Mana Flare, although helping your opponents, will give you gas to drop more dragons.
Gadrak, the Crown-Scourge might work out with
warstorm surge, if you target creatures, would produce treasure tokens for later. Not to mention, that it's a big body for the cost.
Also a lot of the cards that are in your 'Other' section that aren't mana related could be chopped for some of the cards listed above.