http://bugs.winehq.org/show_bug.cgi?id=22987
--- Comment #22 from Vincent Povirk madewokherd@gmail.com 2010-06-01 22:47:13 --- I was mistaken. Both import as CF_DIB.
Anyway, I don't think the clipboard code makes such a "fallback" easy, and I don't understand it well enough to make such a change.
But it should be possible to prefer PIXMAP over image/bmp when both are available. (In fact, I don't know why that isn't the current behavior.)