1984 - Alpha Flight #16 unpublished cover

(http://www.comicartfans.com/GalleryPiece.asp?Piece=807979&GSub=90930)

Here's the original art for the issue #16:

http://www.comicartfans.com/GalleryPiece.asp?Piece=90772&GSub=5668

1983 - Anatomy of a cover - Amazing Spider-Man #243

1983 - preliminary cover for Peter Parker #81

The final cover was drawn by Al Milgrom, but that preliminary cover (grabbed from an issue of Marvel Age) looks like it might have been sketched by Ed Hannigan, or perhaps it is Al Milgrom...

1984 - From The Private Journals of Charles Xavier

Pulled from New Mutants #21-26:

Avengers Universe by John Byrne

From Jim Warden's gallery at ComicArtFans.com (http://www.comicartfans.com/GalleryPiece.asp?Piece=748671&GSub=63580). Wow.

1981 - Captain America #255 - Original Art

Here's seven lovely pencilled pages of John Byrne's retelling of Captain America's origin from Cap #225.
(http://www.comiclink.com/itemdetail.asp?back=%2Fsection%2Easp%3Fid%3D1398%26x%3D6%26y%3D1%26pg%3D5&id=907431)

1977 - Thor pinup by Walt Simonson

Very cool early Thor sketch by Simonson circa 1977.

Found over at http://www.comiclink.com/itemdetail.asp?back=%2Fsection%2Easp%3Fid%3D1398%26x%3D6%26y%3D1%26pg%3D28&id=899966