using DevExpress.XtraTreeList.Nodes;

// Data source for select (left) images.
treeList1.SelectImageList = imageCollection1;
// Use the data source to assign select images to nodes.
// Data source fields do NOT allow you to specify
// two images that depend on the focus.
// This property has priority over the node's
// ImageIndex and SelectImageIndex properties.
treeList1.ImageIndexFieldName = "ImageIndex";
// Data source for state (right) images.
treeList1.StateImageList = imageCollection1;
// Use the Load event to assign images to nodes.
treeList1.Load += TreeList1_Load;

private void TreeList1_Load(object sender, EventArgs e) {
    foreach (TreeListNode node in treeList1.Nodes) {
        // The left image displayed when the node is NOT focused.
        node.ImageIndex = 0;
        // The left image displayed when the node is focused.
        node.SelectImageIndex = 1;
        // The right image that does not depend on the focus.
        node.StateImageIndex = 2;
    }
}

Imports DevExpress.XtraTreeList.Nodes

' Data source for select (left) images.
treeList1.SelectImageList = imageCollection1
' Use the data source to assign select images to nodes.
' Data source fields do NOT allow you to specify
' two images that depend on the focus.
' This property has priority over the node's
' ImageIndex and SelectImageIndex properties.
treeList1.ImageIndexFieldName = "ImageIndex"
' Data source for state (right) images.
treeList1.StateImageList = imageCollection1
' Use the Load event to assign images to nodes.
AddHandler treeList1.Load, AddressOf TreeList1_Load

Private Sub TreeList1_Load(ByVal sender As Object, ByVal e As EventArgs)
    For Each node As TreeListNode In treeList1.Nodes
        ' The left image displayed when the node is NOT focused.
        node.ImageIndex = 0
        ' The left image displayed when the node is focused.
        node.SelectImageIndex = 1
        ' The right image that does not depend on the focus.
        node.StateImageIndex = 2
    Next node
End Sub

using DevExpress.XtraTreeList;

string currentGroupName;
private void treeList1_GetStateImage(object sender, GetStateImageEventArgs e) {
    if(treeList.IsAutoFilterNode(e.Node))
        return;
    string[] groupNames = new string[] { "Administration", "Inventory", "Manufacturing", "Quality", "Research", "Sales" };
    currentGroupName = (string)e.Node.GetValue("GroupName");
    e.NodeImageIndex = Array.FindIndex(groupNames, new Predicate<string>(IsCurrentGroupName));
}
private bool IsCurrentGroupName(string groupName) {
    if(currentGroupName != null)
        return currentGroupName.Contains(groupName);
    return false;
}

Imports DevExpress.XtraTreeList

Private currentGroupName As String
Private Sub treeList1_GetStateImage(ByVal sender As Object, ByVal e As GetStateImageEventArgs) Handles treeList.GetStateImage
    If treeList.IsAutoFilterNode(e.Node) Then
        Return
    End If
    Dim groupNames() As String = { "Administration", "Inventory", "Manufacturing", "Quality", "Research", "Sales" }
    currentGroupName = DirectCast(e.Node.GetValue("GroupName"), String)
    e.NodeImageIndex = Array.FindIndex(groupNames, New Predicate(Of String)(AddressOf IsCurrentGroupName))
End Sub
Private Function IsCurrentGroupName(ByVal groupName As String) As Boolean
    If currentGroupName IsNot Nothing Then
        Return currentGroupName.Contains(groupName)
    End If
    Return False
End Function

using DevExpress.XtraTreeList;

ImageCollection collection = new ImageCollection();
collection.Images.AddRange(new Image[] { img, img2 });
treeList1.StateImageList = collection;
treeList1.GetStateImage += treeList1_GetStateImage;

private void treeList1_GetStateImage(object sender, GetStateImageEventArgs e) {
    if (e.Node.Checked)
        e.NodeImageIndex = 1;
    else
        e.NodeImageIndex = 0;
}

Imports DevExpress.XtraTreeList

Private collection As New ImageCollection()
collection.Images.AddRange(New Image() { img, img2 })
treeList1.StateImageList = collection
AddHandler treeList1.GetStateImage, AddressOf treeList1_GetStateImage

private void treeList1_GetStateImage(Object sender, GetStateImageEventArgs e)
    If e.Node.Checked Then
        e.NodeImageIndex = 1
    Else
        e.NodeImageIndex = 0
    End If

using DevExpress.XtraTreeList;

treeList1.SelectImageList = imageCollection1;

private void treeList1_GetSelectImage(object sender, GetSelectImageEventArgs e) {
    if (e.FocusedNode)
        e.NodeImageIndex = 2;
    else
        e.NodeImageIndex = 0;
}

Imports DevExpress.XtraTreeList

treeList1.SelectImageList = imageCollection1

Private Sub TreeList1_GetSelectImage(ByVal sender As Object, _
ByVal e As GetSelectImageEventArgs) Handles TreeList1.GetSelectImage
    If e.FocusedNode Then
        e.NodeImageIndex = 2
    Else
        e.NodeImageIndex = 0
    End If
End Sub

private void TreeList_CustomDrawNodeImages(object sender, CustomDrawNodeImagesEventArgs e) {
    if (e.Node.Focused)
        e.Cache.FillRectangle(e.Cache.GetSolidBrush(Color.Orange), e.StateRect);
    e.DefaultDraw();
}

Private Sub treeList1_CustomDrawNodeImages(ByVal sender As Object, ByVal e As DevExpress.XtraTreeList.CustomDrawNodeImagesEventArgs) _
    Handles treeList1.CustomDrawNodeImages
    If e.Node.Focused Then
        e.Cache.FillRectangle(e.Cache.GetSolidBrush(Color.Orange), e.StateRect)
    End If
    e.DefaultDraw()
End Sub