Question regarding hex + adding custom sprites

[SolusX]

I have located a couple hex values in Pokemon Black that refer to "empty" sprites and was wondering whether it'd be able to overwrite those sprites with my own somehow. This way I wouldn't have to replace in game characters when inserting custom art.

By empty sprites I mean hex values within the sprites range that produce an invisible sprite. It the value does not redirect to the blue haired generic sprite.