RadAsyncUpload use skins to control its overall look-and-feel. A skin is a set of images and a CSS style sheet that can be applied to the control elements (items, images, etc.) and defines their look and feel. To apply a skin to a RadAsyncUpload set its Skin property, either using the properties pane or the control's Smart Tag.
RadAsyncUpload is installed with a number of preset skins:
The Hay, Forest, Sitefinity and Transparent skins are obsolete and have been removed from the Telerik.Web.UI.Skins.dll assembly as of Q1 2014 .You can find more information on the matter inthis blog post.
If you do not set the Skin property, RadAsyncUpload will automatically use the "Default" skin. If you do not want to use a skin with your control, set its Skin property to an empty string and set the EnableEmbeddedSkins property to false.
You can tweak the existing skins or create your own. Each skin has two main elements: images and a style sheet. When creating your own, it is a good idea to start with the style sheet for an existing skin and alter that. See Tutorial: Creating a Custom Skin for a step-by-step walk through. To use your own skin:
Add the new CSS file to your project.
Drag and drop the CSS file from the Project Explorer onto your webpage.
Set the EnableEmbeddedSkins property of the control to false.
The style sheet for a RadAsyncUpload skin has the name Upload.[SkinName].css and can be found in the ...Skins/[SkinName] directory. The images are found in the ...Skins/[SkinName]/Upload directory. For example, the style sheet for the "Black" skin is called Upload.Black.css and is located in the ...Skins/Black directory. The images are found in the ...Skins/Black/Upload directory. The images are referenced by name from within the style sheet.