Adding custom POI symbols

Hello all. Can anyone guide me how to create custom POI symbols that can be added in the list of default ones on POI editors. POI editing software like Easy GPS, Mapsource, BaseCamp, etc., have the default icons groups sorted from airport to Zoo icons. A couple of software has the option to choose custom icons; however, the displayed custom list shows only blue circles and there is no browse option available to add new icons to the list. Adding BMP through links for each POI entry is time taking when you have a lot of POIs to load.

Is there any way that a couple of custom icons can be added up with the default ones so that selection can be easier and fast.

Thanks.