Jes Goodwin basically designed the Space Marines as we know them... When you talk of Jes, you mainly consider artwork, concept and model design (though not sculpting). He is the head of the design studio and to be honest, is an incredibly talented individual!!!
It was rumoured quite some time ago that Jes was working on Dark Eldar and that the project was taking so long because he wanted to get them "just right"... there was also a few whispers that he was working on "another eldar" project... IE: exodites... though God only knows where this lies these days.
In any case... I think I just heard the Dark Eldar board explode...