Okay, maybe not hiding a spoiler... it's the incentive cover that has a space for hand-drawn shop logos, as an extra level of exclusivity and incentive for comic stores to order extra issues to qualify.
That link also says (from an IDW artist) that the Superion and Devastator on those covers are their Gen1 versions, NOT the current IDW versions... so no spoilers of returned dead characters (on the cover at least).