I played around with it yesterday myself and came up with the attached code, using args.image.image as my changed image source along with some older code It seemed to work OK as well.
Protected Sub RadImageEditor1_ImageChanged(ByVal sender As Object, ByVal args As Telerik.Web.UI.ImageEditorEventArgs) Handles
Dim imgData() As Byte
) = imgData
Public Shared Function ImageToByte(ByVal img As Image) As Byte
Dim imgStream As MemoryStream = New MemoryStream
Dim byteArray As Byte
() = imgStream.ToArray()