http://darkspacecollection.tumblr.com/tagged/space-hulkThis tumblr is gorgeous, full of unused David Gallagher concept art for GW.
The Space Hulk ones reveal some great unused concepts - including Cataphract style terminator armour to distinguish the Lightning Claw armed marine and a mostly bionic body for, I presume, brother omnio.
Also, scenery ideas for a control panel and a genestealer hybrid in a containment/stasis pod.
