Courtesy of Jason Shayer's fantastic blog "Marvel Comics of the 1980's", here are several unused covers to X-Factor #1, featuring the original X-Men reunited for the first time since Giant-Size X-Men #1.
Here's a version by Bob Layton that's very similar to the published cover.
Also, here are some unused costume designs:
This last image doesn't show Jean Grey, because it was printed in a Marvel Age article when her return from the dead was still a secret.
And finally, here is Walt Simonson's final cover art! For more great 1980's Marvel masterpieces, check out