SystemHelper

The icons are looked up by file extension and by "folder", not by reading the files, so the paths need not exist and the lookup is quick. Each call returns a new Icon that the caller owns: put it in an ImageList once per extension rather than per row.

A file browser: the icon for each node from its extension, cached by extension.

var icons = new Dictionary<string, Image>(StringComparer.OrdinalIgnoreCase);

Image IconFor(string path)
{
    string extension = Path.GetExtension(path);
    if (!icons.TryGetValue(extension, out Image image))
    {
        using (Icon icon = SystemHelper.GetFileIcon(path, SystemHelper.EnumIconSize.Small, false))
        {
            image = icon.ToBitmap();
        }
        icons.Add(extension, image);
    }
    return image;
}

foreach (string file in Directory.GetFiles(folder))
{
    BinaryTreeListViewNode node = treeListView.Nodes.Add(Path.GetFileName(file));
    node.Image = IconFor(file);
}