Here's an example that adds a pushpin during the OnClick event of the Map, and sets the Shape's Photo URL to display an image within the InfoxBox.
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
    <title></title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
    <script type="text/javascript" src="http://dev.virtualearth.net/mapcontrol/mapcontrol.ashx?v=6.2&mkt=en-US"></script>
    <script type="text/javascript">
    var map = null;
    function GetMap()
    {
        map = new VEMap("myMap");
        map.LoadMap();
        // Attach the OnClick event
        map.AttachEvent("onclick", OnClick_Handler);
        // You could Dettach the OnClick event like this
        //map.DetachEvent("onclick", OnClick_Handler);
    }
    function OnClick_Handler(e){
        // "sender" is the VEMap that raised the event
        // "e" is the VE Map Event Object
        // Get the Lat/Long where the Mouse was clicked
        var pushpinLocation = map.PixelToLatLong(new VEPixel(e.mapX, e.mapY));
        // Create the Pushpin Shape
        var s = new VEShape(VEShapeType.Pushpin, pushpinLocation);
        s.SetTitle("test pushpin");
        s.SetDescription("test description");
        s.SetPhotoURL("http://i.stackoverflow.com/Content/Img/stackoverflow-logo-250.png");
        // Plot a Shape at the Clicked location
        map.AddShape(s);
    }
    </script>
</head>
    <body onload="GetMap();">
        <div id='myMap' style="position:relative; width:400px; height:400px;"></div>
    </body>
</html>