Got the books earlier this evening. That was faster than I expected!
It'll take me some time to properly go through these. I did notice a bunch of sketches near the middle of the Mega Man Offical Complete Works book (page 118 and 119) of Robot Masters that weren't used for Mega Man II, and though many were just evolutionary steps to the finalized Robot Masters we're familiar with, many of them really could pass as Robot Masters as they are. It's funny to see that their names go through changes, too, and there are some names and designs that would appear in later games.
On the road to Bubble Man, there's a design called Pump Man (the name of a Robot Master in the upcoming Mega Man 10), several Water Men including a fishy one that looks like Neptune (from the Game Boy Mega Man V), and it looks like Bubble Man himself was also almost called Water Man, a name strangely not used yet. Before Air Man is a prototype Wind Man, who looks like Elec Man and nothing at all like his Mega Man 6 namesake. Metal Man could have been called Rolling Man, and strangely enough, a previous version of him actually has his finalized name. Wood Man is grouped together with a bunch of animal "Men", including Hornet Man, a name used in Mega Man 9. Crash Man could've been named Missile Man, and his previous form was called Drill Man, who actually looks close to the Mega Man IV version. Heat Man resembles a lighter, but his precursor is Smoke Man, who has a cigarette in his mouth; I'm not too sure that would go over well in America considering Capcom themselves didn't like Wesker smoking in the live-action opening of the already M-rated Resident Evil for the PlayStation.
There's also a silly coloured sketch of a red guy with a magnet on his head who is unused, but bears a resemblance to Magnet Man in Mega Man III. And wow, all that interesting stuff on just two pages. Four pages later, there are tons of unused Robot Master designs, most don't have names, unfortunately. Of the few named ones, Vacuum Man looks a lot like Pump Man from the first page I mentioned.
And of course all the official finalized artwork is amazing. They also have box art; somehow they have an entire page for each of the first two European boxes, and while they also have the American Mega Man II/2, they seem to have deliberately omitted the American box art for the first game.
Unless I missed it...
