A have two pictures in my resources:

:/images/logo_small.png
:/images/logo_small@2x.png

When I define background property on widget:

#widget2{
background-image: url(":/images/logo_small.png");
}

On retina display small image with no antialias drawn. In this situation will be drawn logo_small@2x.png image.

When I define image as icon all works fine. This bug appear only on stylesheets.
Example project in attachment.