Scott Summers and Jean Grey by Bill Sienkiewicz

Scott Summers and Jean Grey by Steve Rude

1983 - Anatomy of a cover - Uncanny X-Men #174

1986 - X-Factor character design Cyclops

http://www.comicartfans.com/GalleryPiece.asp?Piece=336457&GSub=52596

1986 - Anatomy of a cover - X-Factor #13

Grabbed from the Walt Simonson Appreciate Society Facebook page:

"X-Factor 13 cover. Pen and India ink. 10 x 15. 1986."

"Apparently, I drew this picture around the logo and corner box somehow, but no idea how I did it now. There are some cut lines on the cover, really more grooves, along the perimeter of the logo and corner box. In the printed version, there's a little bit of drawing over the logo itself. So it may be that the logo was added first, and then I did the final inking.  It's a mystery. 

1989 - X-Factor headshots for the Official Handbook of the Marvel Universe

From the Walt Simonson's Facebook albums:

"X-Factor's original members. Pencil. 9.5 x 15. 1989??. Found this as I was rummaging around for something else. These are the pencils for the portraits of the characters that appeared in the X-Factor entry in the Official Handbook of the Marvel Universe. (Thanks to various folks who were able to identify the drawings, where I was clueless. )"

And here's the published version: