I tried to check this out through the discussion on proposed improvements concepts, but my eyes gave out, so here's this:
As a guy who is all over the printed materials relative to the retro stuff, and have a lot on hand to scan, it would be nice to reprise some of the great stuff color printed as game instructions.
I'm going to assume the reason that can't be entered is that there isn't the band chops to carry it?
There are fantastic printed color graphics instructions for games like Operation Crusader, but no mechanism for entry. Seems a shame. I did just this morning enter the allowed 'inside cover' for EA's Delta Patrol. But my scanned Manual pages of cool color graphics for the Crusader game, and the Map matrix got the heave ho.
You might want to check out Replacementdocs, which is specialized on documenting manuals. Just like the distribution of freeware games and patches, it is outside of our focus. This is unlikely to change.
However, when the extra images section is implemented (it is "coming soon" for at least five years, so I wouldn't hold my breath), scans of the manual front cover may be allowed. But that is a complete speculation on my part.