Bug report: The Full Heall item ball next to the exit inside Viridian forest reappears after it is taken, resulting in infinite access to full heal.
As for sprites, this may be a taste thing, but you said you are going to redo the sprites, so I'll mention it. Red's cap has a white front (in this case, on the back of his head since he wears his cap backwards).
I don't know if this is intentional or not, but Pallet Forest and Viridian Forest don't have wild pokemon (at least as far as I've gotten, which is before catching Pikachu).
Another thing, Red's Poli and Pika are male. The ones I have are female, so either they're set on random, or they're set on female (not sure if this is controllable, since I'm not a hacker).