You don't have to package anything, that's the benefit of using bundles, just change the bundle icon with your game icon, put the game in the bundle and make sure it gets loaded.

This is an interesting question, how many image formats a game engine needs? Technically speaking, one format is enough, just "save as" your artwork in this format and you'll be fine. On the other hand, to port to Nintendo platforms you need to be a registered Nintendo developer, so you ca...