How can I set an icon for a ListViewSubItem?

The ListView control does not support images in sub-items natively. The easiest thing to do is switch to a DataGridView and use a DataGridViewImageColumn. If that is not possible, then you'll need to draw the icons yourself using the custom draw support in the ListView control. To do this set ListView.OwnerDraw = true and handle the ListView.DrawSubItem and ListView.DrawColumnHeader events.

private void listView1_DrawSubItem(object sender, DrawListViewSubItemEventArgs e)
{
    // Only interested in 2nd column.
    if (e.Header != this.columnHeader2)
    {
        e.DrawDefault = true;
        return;
    }

    e.DrawBackground();
    var imageRect = new Rectangle(e.Bounds.X, e.Bounds.Y, e.Bounds.Height, e.Bounds.Height);
    e.Graphics.DrawImage(SystemIcons.Information.ToBitmap(), imageRect);
}

private void listView1_DrawColumnHeader(object sender, DrawListViewColumnHeaderEventArgs e)
{
    e.DrawDefault = true;
}

Use P/Invoke and send LVM_SETITEM message to the listview (you should set LVS_EX_SUBITEMIMAGES style on control creation or via LVM_SETEXTENDEDLISTVIEWSTYLE), specify the subitem index and the corresponding image index. You will need to do it for every list item you insert.

ObjectListView is an open source wrapper around a .NET Winforms ListView. It supports images on subitems using the p/invoke strategy that that @ligget78 mentioned. It also solves many other common problems with a ListView.

It allows you to make very nice looking ListViews with a minimum effort:

_{(source: sourceforge.net)}

Inherit from ListView and draw your own icons.

public class MyListView : ListView
{
    protected override void OnDrawSubItem(System.Windows.Forms.DrawListViewSubItemEventArgs e)
    {
        base.OnDrawSubItem(e);
    }
}