Instead of using the defined background colors for the tree control, a user-defined bitmap can be displayed in the client area of the tree control (see the BackgroundPicture property).  If the background bitmap is too small to fill the entire client area of the tree control, it is tiled (depending on the BackgroundStyle property).  The row header area, row/column header area and column header do not display the background bitmap.  These areas are not transparent.

There is no default background bitmap. Bitmap transparency is not used for the background bitmap.

The background bitmap is not used when displaying cell ToolTips.