How extreme is too extreme on video game box art? Looking at the two pictures above, there's nothing in either of them that would raise alarm bells for an adult or even a teenager/older child. The ERSB disagrees, claiming that the red spray behind the skull could in fact be misinterpreted as blood. This is in violation of their advertising guidelines.
In North America the red colour has been removed for a far more mellow sea blue. It seems an odd thing to have changed, considering the hole in the skull remains (although it seems the "damage" has been toned down, leaving a gaping hole instead of what looks like an intentional injury). Still, neither image is especially bad and this will probably be blown out of proportion by the vast minority for a couple of days and then be forgotten about when the game is launched at the end of next month.
Deep Silver had a previous run in with the ERSB after depicting a hanging corpse on the cover art for Dead Island. That was also changed before release.