Your suggestion is very good but I'm afraid it is not included in our current plans. We will consider it and eventually include it in our future plans.
For the time being I can recommend you to use templates or the ImageUrl property of the RadComboBox.
the Telerik team
for the Q2 2011
What’s New Webinar Week. Mark your calendar for the week starting July 18th and book your seat
for a walk through of all the exciting stuff we will ship with the new release!