I'm not sure. What it does do is put a black bar where the image should be (See Screenshot). You'll notice I have other images that just have a question mark place holder. That's because the src url's on those are definitely wrong.
I've seen the black bar thing before. When I added a iconCls to a button. I didn't apply the @include pictos-iconmask(myicon) so the image wasn't showing up.
So I've included that mixin again for this image but still nothing.