RE: Cornelias's Spritez
You're still saving as .jpg files instead of .png, which is leaving your sprites pixelated and compressed.
As for the design behind Mega Regirock, it still looks a little TOO similar to Regirock. While some Megas are merely the regular Pokémon with a few added touches (i.e. Mega Ampharos), many bring more physical changes to the Pokémon (Mega Alakazam, Mega Gengar). Mega Evolutions also tend to exaggerate the design points of the Pokémon that were already exaggerated...on Regirock, for instance, I would've enlarged its club hands/arms and orange shoulders. Additionally, why would a Pokémon made of rock (with club-like arms) evolve to have claws? It's primarily a defensive Pokémon anyway, so you could take it a step further and make it more bulky-looking.