Hello.
For this purpose use setImageUrl method: #{imgPicture}.setImageUrl( "../Resources/blank.png");
Example:
<html>
<head runat="server">
<title>Pan Image - Ext.NET Examples</title>
</head>
<body>
<form runat="server">
<ext:ResourceManager runat="server"/>
<ext:Window
ID="Window1"
runat="server"
Title="The Universe Map"
Icon="Map"
Width="800"
Height="600"
Shadow="false"
Layout="Fit">
<TopBar>
<ext:Toolbar runat="server">
<Items>
<ext:Button runat="server" Text="Change image">
<Listeners>
<Click Handler="#{Image1}.setImageUrl('http://www.jeremykratz.com/_/img/extnet-logo.jpg');" />
</Listeners>
</ext:Button>
<ext:ToolbarFill runat="server" />
<ext:Label ID="LabelStatus" runat="server" Text="Status: " Width="100" />
<ext:ProgressBar ID="Progress1" runat="server" Width="200">
<Listeners>
<AfterRender Handler="this.wait({interval: 200, increment: 15, text: 'Loading...'});" />
</Listeners>
</ext:ProgressBar>
</Items>
</ext:Toolbar>
</TopBar>
<BottomBar>
<ext:StatusBar ID="DeltaStatus" runat="server" />
</BottomBar>
<Items>
<ext:Image ID="Image1" runat="server"
AllowPan="true"
XDelta="-4555"
YDelta="-3286"
ImageUrl="http://sodeve.net/wp-content/uploads/2011/02/ext.net_.png">
<Listeners>
<Complete Handler="#{Progress1}.reset(true);#{LabelStatus}.setText('Status: Loaded');" />
<Pan Handler="#{DeltaStatus}.setStatus({text: 'X: '+x+' Y: '+y});" Buffer="100" />
</Listeners>
</ext:Image>
</Items>
</ext:Window>
</form>
</body>
</html>
