want to show default image if ajax slideshow extender does not return images from database? ?

hi,
Images/DefaultImage.jpg
i want to show above default image if the slideshow extender code I am working with does NOT return any
images from database?
should there be an else clause somewhere

ASPX

                            <cc1:SlideShowExtender ID="slideshowextend1"                 TargetControlID="imgShowImage"                 SlideShowServiceMethod="GetSlides"                 AutoPlay="true"               ...