http://www.karcreat.com/HowardTrailer.html
There's also a better quality than Youtube version of the video at:
http://www.karcreat.com/HTDMP3Download.html
(Karcreat's site has some MP3 stuff as well, including the title song)
There were a ton of radio ads for this as well, the angle was "Who's Howard?" to try to stir up some interest about the character to people unfamiliar with the comic. There was also Topps candy Howard's and a read-along storybook I believe. Any and all of these things would be fun to add to the DVD if we can track it down.
Also, there was the Commodore 64 game, which was actually a sequel to the film. I used to have this in the original box. Here's some info:
http://www.lemon64.com/index.php?mainurl=http%3A//www.lemon64.com/reviews/view.php%3Fid%3D709
Here's the great promo ad for the game: http://www.lemon64.com/index.php?mainurl=http%3A//www.lemon64.com/reviews/view.php%3Fid%3D709
Here's an article about Howard-related subway graffitti in 1980s New York City: http://www.mcny.org/collections/painting/pttcat116.htm
(You can see this briefly in the film Style Wars as well)
The way I look at it, is let's load this thing up with as many special features as possible, since we probably will never get an official release. Maybe even include the "I Love the 80s" VH1 segment about the film that featured Lea Thompson as well. Text