This is pretty cool. I like it.
Other cards you could add to enhance the whole "
Sprite Dragon" gameplay are
Pyroceratops,
Spellgorger Weird, and - most importantly -
The Ozolith.
I find that this kind of deck that relies on counter buildup as a win con is really susceptible to
Flicker or
Unsummon type spells, as they wipe the counters.
The Ozolith can compete with these, letting you simply plop the counters back onto another creature.
(I hope this is useful, though it's just a suggestion.)