How to delete picture box image property in a custom control at design time

I am creating a windows mobile 6.1 application in VS2008 and I am creating a custom control that will use the picture box control.  I expose the image property of the picture box by using a property tag.  After compiling the code and adding the control to my project's form, the picture box image is initially blank but if I set it I must do it via the open dialog box (same as if just using the regular picture box).  The problem is when I want to delete the image (if I made a mistake and do not want to include the image just have a blank picture box, it does recognize that the delete key was pressed in the property field.  The only access to change the value is via the open dialog box and that requires a file to be selected.  Attached is a code snippet of the property tag for to expose the image.  Any help is greatly appreciated.

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    Public Property Position1Picture() As Image
        Get
            Return picPosition1.Image
        End Get
        Set(ByVal value As Image)
            picPosition1.Image = value
        End Set
    End Property