http://bugs.winehq.org/show_bug.cgi?id=22987
--- Comment #16 from Vincent Povirk madewokherd@gmail.com 2010-06-01 09:03:49 --- Irfanview is not at fault here. Wine is not getting valid bitmap data itself, so it can't pass that along to the application.
I'm seeing the same results as Dmitry here. The image/png target does work, however. Still, I maintain this is not a Wine bug.