Well I've got different "headers", they look like this for example:
(maybe the engine symbol needs to be a bit less massive and the speedometer symbol a little less delicate, but the artwork for this CarDuino is all still in progress).
So the top 25 pixels of each screen will look very similar, but then again, they will be slightly different depending on which sub-menu you're in.
I've already put a boolean variable in the code that gets switched when the header and the icons for a submenu have been loaded, so that they don't flicker all the time because they're being loaded again. The only dynamic parts of a screen will indeed be the changing sensor readings and calculated values. At a rate of about once every three seconds.