How to add images/icons  in  WPF Tree View from code behind

Following is my WPF code, can someone guide me how can I add images from
codebehind

<TreeView Grid.Row="2" FontFamily="Courier" FontSize="14" Name="tree"
TreeViewItem.Selected="TreeView_ItemSelected"
TreeViewItem.Expanded="TreeView_ItemExpanded" >

</TreeView>

<TreeViewItem FontFamily="Courier" Foreground="Red" Background="Yellow"
FontSize="14" />

....

TreeViewItem Newitem = new TreeViewItem();

Newitem.Tag = cNodeSite + u.SiteID.ToString();

Newitem.Header = u.SiteName.ToString();

Newitem.Foreground = System.Windows.Media.Brushes.Green;

Newitem.Items.Add("*");

item.Items.Add(Newitem);

tree.Items.Add(item);

....

....

Thanks

DNB