Φίλε,
για δοκίμασε να αλλαξεις την GetEmbeddedPng και κανε return Type Image αντί Bitmap
Function GetEmbeddedPng(ByVal strName As String) As System.Drawing.Bitmap
      Dim mybitmap As New System.Drawing.Bitmap(System.Reflection.Assembly.GetExecutingAssembly.GetManifestResourceStream((strName)))
      Return mybitmap
End Function
σε
 
Function GetEmbeddedPng(ByVal strName As String) As System.Drawing.Image
      Dim mybitmap As New System.Drawing.Image.FromStream(System.Reflection.Assembly.GetExecutingAssembly.GetManifestResourceStream((strName)))
      Return mybitmap
End Function
Ίσως φταίει 
το transformation  σε bitmap.
just a thought!
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