BCGControlBar Pro for MFC
UINT BCGM_GET_TOOLTIP_IMAGE_SIZE

The message is sent to the parent of CBCGPToolTipCtrl object.

Parameters
wParamthis parameter is not used.
lParama pointer to CSize object which contains a tooltip image size.
Returns
should return nonzero if a custom image size was specified.

You should process this message if you wish to draw a custom image (icon) on the tooltip control.