1983 - Moon Knight Portfolio by Bill Sienkiewicz from Moon Knight Special Edition #1

1983 - Ad for Michael Golden's Dr. Strange Portfolio

From the Comics Journal #81

1984 - Cloak and Dagger Portfolio by Rick Leonardi and Terry Austin

1985 - Ken Stacy Portfolio I

From Marvel Fanfare #22.

1980 - Incredible Hulk portfolio

1980 - Spider-Man portfolio - Updated

 

1980 - X-Men Portfolio Set 1

1982 - Marvel Team-Up Portfolio Set Two (Updated with better pics!)

 

Six black-and-white 11-in. x 14-inch plate published by S.Q. Productions in 1982.

Spider-Man and the Thing vs Thanos: By Thanos Vanquished (by Alan Weiss and Joe Rubinstein)

Spider-Man and Thor vs the Living Monolith: In the Hands of the Living Monolith

(Bill Sienkiewicz/Tom Palmer)

Spider-Man and Nick Fury Agent of S.H.I.E.L.D.: If S.H.I.E.L.D. Should Fall (Ernie Colon) 

Spider-Man and Uncanny X-Men: All Against the Lords of Light and Darkness (George Perez)

Spider-Man and Dr. Strange: To Win the Wand of Wattomb (Frank Miller/Craig Russell) 

Spider-Man and Silver Surfer: When Rides ... The Silver Surfer (John Byrne/Terry Austin). 

1981 - Marvel Team-Up Portfolio Set One

Published by S.Q. Productions in 1981. Six all-new illustrations on black-and-white 11-in. x 14-inch plate. (Sorry for the mediocre quality, but they were the best I could find!)

Spider-Man versus Daredevil (by Frank Miller and Klaus Janson)

Spider-Man and Daredevil and Thor vs Fantastic Four: The Flames of Battle (John Byrne/Terry Austin) 

Spider-Man and the Defenders: On the Trail of the Lunatik (Michael Golden) 

Spider-Man vs. the Hulk and the Green Goblin: Green Death (Walt Simonson) 

Spider-Man and Man-Thing vs D’spayre: Behold D’spayre (Brent Anderson)

Spider-Man and Iron Fist & Power Man (Kerry Gammill)