Would I be correct in saying, if you have a few medium size images (larger than buttons) that do no get used in every screen, then it may be better off leaving them as an image and not trying to import into a spritesheet?
That is, in terms of sprite sheets, aim to put in the small-medium sized images that get used repeatedly as a strategy?
i.e. if you put medium sized images into your main spritesheet then it may be bigger than it needs to be, and this would be across all screens?