i think as long as they are from a game made by actual companies/developers (eg. the old shadow the hedgehog flash game from like 2006, cave story, etc.)
although i think if its a fanmade game (every sonic, mario, etc. flash game not licensed by their company) the original creator of the sprites needs to submit the sprites themselves
although i think if its a fanmade game (every sonic, mario, etc. flash game not licensed by their company) the original creator of the sprites needs to submit the sprites themselves