Actually they don't show in Ripple emulator because they work on the devices. :)
WebKit masks which we use to render our icons are completely broken in BBOS 7.0 (though they were fixed in BBOS 7.1). This led us to do a workaround there - the masks do work in a specific case - when they are applied on a transparent background, they show the original PNG image from the file. However the said workaround works okay in Ripple (different browser engine) and render the masks transparent, hence no icons.
the Telerik team
Join us on our journey to create the world's most complete HTML 5 UI Framework - download Kendo UI