Okay, a few things:
First off - nice image update. The art reminds me of a Fire Elemental being just spewing flames from his mouth onto your creatures, which must hurt like hell.
With the card itself, DON'T make it stack - considering that -2 | -1 is a 'status' effect, having it 'stack' would mean that you're either a) killing it (making it like a special version of Sniper from Eagle's Eye, and b) would cause low attack creatures to obtain -attack values (which would make it work like a form of antimatter, which doesn't make sense).
Actually, would this card drop a creature with 0 or 1 Attack to -2 or -1 attack, thus healing you if they attacked? Or not? Either way, the card is a nice idea, but I think Flamethrower feels a little bit odd to place in the Elements Game as a weapon. I keep on thinking of the artillery weapon, which doesn't quite fit still...