If you name an icon .bmp the same as your POI file name (such as MyFinds.gpx, and MyFinds.bmp) and put it in the same folder, upon uploading you will get this custom icon displayed.
Where can I get the "GeoCache.bmp" and GeoCache Found.bmp" files to associate with my custom POI files. I've tried xlimage to get them off my vista cx, but it just pulls the blue dot custom icons off. I've looked at downloads throughout the net with no luck. I'd like the Garmin originals to match my vista icons.