Question Can i fully cover gpu backplate with vinyl sticker?

I would not put a sticker on the backplate.

Not sure if and how the sticker might affect cooling but not worth the risk.

Besides, if a sticker was viable and/or warranted, the manufacturer probably would have stuck on their own sticker. Marketing stuff....

Leave well enough alone - do not let form (cosmetics) get in the way of function.

Just my thoughts on the matter.

(And a sticker could invalidate warranty.....)