This is because your code inserts the picture twice. Try:
Code:
With Application.Dialogs(wdDialogInsertPicture)
If .Display = -1 Then
If .Name <> "" Then
Set Photo = ActiveDocument.InlineShapes.AddPicture(FileName:=.Name, _
LinkToFile:=False, SaveWithDocument:=True, _
Range:=Selection.Range)
End If
End If
End With