I understand that a band's artwork has nothing to do with their sound. But Angst Skvadron's album cover for their 2010 release Sweet Poison. Will cause a lot of potential fans to skip right over it.
Oranssi Pazuzu, but I see this type of black metal taking off. Even much of their lyrics are focused on aliens, they even make use of the theremin to make spaceship noises. They've been out there since 2008 releasing two albums and two EPs(both from 2010).