VB.net/c# HowTo add bitmap's to your user controls

[Andy]

If you've ever created a user control, particularly an inherited control, you've noticed that the icon to the left of your new control in the toolbox is simply a gear. With the below code, you can add the icon from an existing control:

<ToolboxBitmap(GetType(System.Windows.Forms.TextBox))> _
Public Class TextBox
    Inherits System.Windows.Forms.TextBox
 
End Class

or in C#

[ToolboxBitmap(typeof(Button))]
class MyControl1 : UserControl
{
}

more information can be found Here