set to true the OwnerDrawNodes and then handle the BeforeNodePaint event as follows. This paints the image at the left of the control, but I find it may be preferable that being next to the left of the text.
private void treeCustom_BeforeNodePaint(object sender, Syncfusion.Windows.Forms.Tools.TreeNodeAdvPaintEventArgs e)
{
Rectangle clientRectangle= e.Bounds;
Point TextLocation=e.TextLocation;
if (TextLocation.X