I found a CSS driven gradient work-around for my particular scenario. In case anyone is interested, this will give the same effect I desired:
.TelerikModalOverlay {
background-image: -webkit-gradient(linear, left top, right bottom, color-stop(0, #bbb), color-stop(0.25, #bbb), color-stop(0.25, #aaa),
color-stop(0.5, #aaa), color-stop(0.5, #bbb), color-stop(0.75, #bbb), color-stop(0.75, #aaa)) !important;
background-image: -webkit-linear-gradient(left top, #bbb 0%, #bbb 25%, #aaa 25%, #aaa 50%, #bbb 50%, #bbb 75%, #aaa 75%) !important;
background-image: -moz-linear-gradient(left top, #bbb 0%, #bbb 25%, #aaa 25%, #aaa 50%, #bbb 50%, #bbb 75%, #aaa 75%) !important;
background-image: -ms-linear-gradient(left top, #bbb 0%, #bbb 25%, #aaa 25%, #aaa 50%, #bbb 50%, #bbb 75%, #aaa 75%) !important;
background-image: -o-linear-gradient(left top, #bbb 0%, #bbb 25%, #aaa 25%, #aaa 50%, #bbb 50%, #bbb 75%, #aaa 75%) !important;
background-image: linear-gradient(left top, #bbb 0%, #bbb 25%, #aaa 25%, #aaa 50%, #bbb 50%, #bbb 75%, #aaa 75%) !important;
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#aaaaaa', endColorstr='#bbbbbb',GradientType=0 ) !important;
background-size: 30px 30px !important;
width:100% !important;
height:100% !important;
filter: alpha(opacity=70) !important;
opacity: .70 !important;
-moz-opacity: .70 !important;
}
I would still be interested in an image as well if anyone knows how to achieve this.
Regards,
Steve