you can use ur images to be loaded from an url... that way no images will be exported... but the empty sprites.. however... will kinda be hard to do an animations like that.. cause on each frame you will have to load a specific url .. but then if u dont have any animations (as in games) but you want to make apps... software functionalities and ul have only a bg and some effects around... that will do the trick ...
not sure if u can load full sprite sheets in a sprite to be used as an animation from an url... never hit that wall
can i ask why u want the images no to be exported? outside that "i want to manage the quality and size " <- never heard that one sorry XD i might be a weird one
if u think ur png files are to big and to heavy.. you can try different software's as tinypng[dot]com . or using a hard compression from Photoshop exporting?
just an idea ... dont want to be rude...