I'm guessing it'll be that "art" card some of the sites show, rectangle shape with white background and the band in dark (black?) clothing. I know I've seen it on some site with it next to the vinyl. Of course, that doesn't mean they are showing the card in proportional size to the vinyl.
The art cards I have seen where advertised as A5 (Loudersound, Kerrang) or as postcard (HMV), which is usually a smaller A6 format.
There were different designs shown which looked to come from the same photoshoot. Loudersound showed a colored photo while Kerrang has a b&w and different pose.
The relative size here compared to the vinyl is correct to A5 (this is from Loudersound).