I assume you want to clear the Images drawn via PictureBox.
This you would be achieved via a Bitmap object and using Graphics object. you might be doing something like
Graphics graphic = Graphics.FromImage(pictbox.Image);
graphic.Clear(Color.Red) //Color to fill the background and reset the box
Is this what you were looking out?
EDIT
Since you are using the paint method this would cause it to be redrawn every time, I would suggest you to set a flag at the formlevel indicating whether it should or not paint the Picturebox
private bool _shouldDraw = true;
public bool ShouldDraw
{
get { return _shouldDraw; }
set { _shouldDraw = value; }
}
In your paint just use
if(ShouldDraw)
//do your stuff
When you click the button set this property to false and you should be fine.