I just tagged all the Osu! Tatake! Ouendan pics with ouendan (and the sequal's wallpapers with ouendan_2, since the full title is beyond my certainty).
In checking the sequel's title, I saw that "ouendan" is a generic term as well, but briefly parlancing some of the tag's pics, I'm not sure what it's [meant to be] used for, and there's no wiki.
Updated by 0xCCBA696