That is indeed an early concept boxart for the cancelled Megaman Anniversary Collection, but erroneously has Ground Man present, who only appeared in Megaman & Bass. The image looks like it was later used with Groundman being replaced by Skullman.
Buyatari, these American treasures are not found in any Megaman artbook, not even the excellent R20 which has hundreds and hundreds of sketches. Please, I implore you, please scan each of your amazing sketches and add them to an archive without watermarks!
What you have is truly exciting. The Sketches of the US boxarts for the Gameboy games alone gets to me.