Yes, you could achieve such an appearance for RadComboBox using custom skin. In this case I think it is better to start to define the styles on your own, instead of using the Visual Style Builder.
You should keep in mind that you should provide your own images which will have the right size for the appearance you want to create for RadComboBox.
The following help article could be a good startup: http://www.telerik.com/help/aspnet-ajax/combobox-appearance-creating-custom-skins.html
I hope this will help.
the Telerik team
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