True to my manhood I choose artwork, because its prerequisite for me before considering fapping to it. In such case I've got many gorgeous stillshots for fapping, from the *danbooru sites.
But there is something kind-of-story-line-ish that is just as important as art to me. I don't know what to call it, mood and content seem appropiate.
If it is non consensual, scatological, violent, overtly abundant in dicks or mechanical and completely lacking in emotional aspect, I pass.
Conversely, give me some hot sweet girl on girl lovin' and I'll make fakku my homepage.
Edit: Uhmm I don't know about artist, I don't notice while fapping. Two of my favorites are Carnelian and Rokku but I'm sure I've fapped to some very doujins with similar artwork before, I'll take note from now on.