for a sample to use ..you can draw a line using basics only...
how to set canvas backgroud as image..
ImageBrush ib = new ImageBrush();
ib.ImageSource = new BitmapImage(new Uri(@"sampleImages\berries.jpg", UriKind.Relative));
mycanvas.Background = ib;
and you can now draw on your canvas a line like this..
line = new Line();
line.Stroke = Brushes.LightSteelBlue;
line.X1 = 1;
line.X2 = 50;
line.Y1 = 1;
line.Y2 = 50;
line.StrokeThickness = 2;
myCanvas.Children.Add(line);
hope it will help you to start..