Here is what the cover to Bili the Axe: Up Harzburk! might have looked like had it been done by Metagaming for TFT rather than GURPS, in a nicer timeline. Note that this would likely have been in a larger "MetaGame" box like Dragons of Underearth and probably the planned Conquerors of Underearth module. It is to be noted that CoU was intended to feature mass combat, which is also a focus of Up Harzburk.
Note that the original adventure as released was deeply flawed and unplayable due to some of the numbered paragraphs being incorrect, too many to be addressed by errata. I have given thought to trying to find and correct these errors, and turn it into a playable module, though that might be too difficult a job.
Anyway, here are the revised covers: