MessageBox is usefull, but no! You cannot put an image other than the ones provided into it. No problem: create a Form class to imitate the behaviour of the message box. Because it would be a class of your own design, you can do in it what you want;)
For Each ctrl As Control In Me.Controls("pnlMainPanel").Controls
If ctrl.GetType Is GetType(System.Windows.Forms.Panel) Then
For Each subCtrl As Control In ctrl.Controls
If subCtrl.GetType Is GetType(System.Windows.Forms.TextBox) Then
If subCtrl.GetType Is ...