Just Five?!?!?! That's a cast iron Bitch, that. But I actually thought about this one, so....
1 - Santana - Abraxas
<img src="http://images.amazon.com/images/P/B0000062FL.01.LZZZZZZZ.gif">
2 - Frank Zappa - Overnite Sensation
<img src="http://www.musicmatic.de/Z/Zappa__2a.jpg">
3 - Gentle Giant - Octopus (UK cover by Roger Dean)
<img src="http://mitkadem3.homestead.com/files/Gentle_Giant_Octopus_UK_CoverJPG.jpg">
American cover was pretty nifty too:
<img src="http://www.progreviews.com/reviews/images/GG-Octo.jpg">
4 - Grateful Dead - Blues for Allah
<IMG SRC="http://thebestofwebsite.com/Photos/Music/Grateful_Dead/Studio/Blues_for_Allah.jpg">
5 - Iron Maiden - Somewhere in Time
<img src="http://www.aumi.de/music/ironmaiden/somewhereintime-gross.jpg">
6 - Yes-Tales From Topographic Oceans
<img src="http://www.cnn.com/interactive/entertainment/0205/yes.albums/tales.jpg">
7 - King Crimson - In the Court of the Crimson King (see picture in Follthemall's post below)
8 - Blue Öyster Cult - Cültosaurus Erectus
<img src="http://www.tangento.iwarp.com/cultosaurus.jpg">
Oops.
(edited to add pix)