Questions questions questions! You're the never ending question machine it seems! 
 
Ryan Clark are Ed Repka are probably among my top artists/designers I guess. I tend to like more minimalist artwork if anything, or at least artwork that is more matte and/or less immediately intricate. Spheres, symmetry and space imagery are also favorites for me.
Trenches - 
The Tide Will Swallow Us Whole
The Analyst - 
Summoning the Wretched
Cloudkicker - 
Fade
Cloudkicker - 
Hello
August Burns Red - 
Messengers
Distances - 
Ages
Tesseract - 
Altered State
Winters - 
...And Bear Witness to the Colossus...
Becoming the Archetype - 
Dichotomy
Red Seas Fire - 
Exposition
Buried at Sea - 
Ghost
Hollow Tongue - 
Godsnakes
Lost in Kiev - 
Motions
The Famine - 
The Raven and the Reaping
The Famine - 
The Architects of Guilt
Callisto - 
True Nature Unfolds
Demon Hunter - 
Storm the Gates of Hell
Hugi - 
Solarliod (PS: This album is some super fucking shitty black metal and I regret buying it but god I love the design work, which honestly made me think it wasn't even a black metal band to begin with, lol. Also, I had horrible time even finding good digital artwork when I ripped it so this is actually my scan of it)