Sorry for the double post, but some more came to mind after posting the one above!
Can't believe it was only THEN that I thought of them... *facepalms* O.O
And sorry for the 'Abbey Road' mentioning, only saw it was on page 1 of the thread after I posted my previous post...
Ahum... allright, here we go!
"Rage Against The Machine - "

One of the most powerful and politically influenced album covers of all times... it still is one of my alltime favorite bands! ...and that's not only because of their neverending stamina to keep on 'bashing the power in their golden tower'!!
\\m/_ _\\m/
"Guns 'n Roses - Appetite For Destruction"

One of those album covers that are recognised instantly all over the world! Even by people who are not a fan... =P
"Prince - Lotus Flower"

The colours and imaging used on this album cover make for a beautiful picture to look at! The music on it was so-so...
And last, but most of all NOT LEAST...
"Van Halen - 1984"

To me, one of the best albums ever made! Not only of this particular band, but also for the entire music available and that I've been able to listen to so far! PLUS, it's (again) an album cover that is recognised by a lot of people when shown to them, even if they are not a fan... =)