Hello John Heins,
It depends on where the data is stored.
If this is an image from Sitefinity Image Gallery you could use [provide]Guid - [Libraries]29ac180f-e615-4b43-9835-b003a5f11f46
If you use an item uploaded to a directory in your project you could pass the relative path (~/Images/menu.jpg).
The better option is storing the items to Sitefinity Image Gallery and passing the [Provider]Guid value. This will ensure that renaming the image will not break any links.
the Telerik team