You are an illiterate bastard (and you're talking a lot poop)
He's talking about CSS sprites and changing the image on hover via the background-position property. Way to over complicate things. However, considering the developers want to make things 'customizable', I would recommend having text-based navigation instead. That way it would cut down on both load time, bandwidth and increase in portability. Don't rely on JavaScript for everything.
And what is this shenanigans about "already had it cached" ?? It's an image! Unless you are talking about preloading the image. Hahahaha. If you are talking about cache for real, then you should be referring to Expires Headers in the .htaccess, gzip compression, etc.