You can configure the view and upload paths of the Image Manage which is opened from the Page Properties dialog using the highlighted properties:
<telerik:RadEditor runat="server" ID="RadEditor1">
<ImageManager ViewPaths="~/Images" UploadPaths="~/Images"
This will enable the upload dialog and the user will be able to upload images from the hard disk and insert them as a background image via the Page
In the ViewPaths property specify a directory especially created for the logged user.
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