The only major imageboards are 4chan and Futaba, to be completely honest. Most of the imageboards that are referred to as "major" don't generate enough traffic to be categorized as such. They're like the cream of the crop of B-movies. And besides, the only other imageboard moot's even acknowledged existance of to date was 7chan, and that was only to quell rumors that he was buying it, and to openly call it a piece of shit.

If you call 711chan major, your standards of what's major and what isn't need some adjusting.