Probably the best way to maintain clean code is to create an extension method, also note that your second picturebox is currently not added to controls.
public static class MyExtensions
{
public static PictureBox CreateNewWithAttributes(this PictureBox pb)
{
return new PictureBox { Image = pb.Image, Width = pb.Width };
}
}
Picturebox p2 = p1.CreateNewWithAttributes();
this.Controls.Add(p2);
More can be read on extension methods here