Hi Chris,
I just bought the pro version and have installed the latest beta. There is no/icons/ subdirectory in the root of the MapPress plugin directory of the beta version.
There is an /icons/ subdirectory in the non-beta Pro version. I have tried creating the directory and added a png file, but nothing is showing up either on the wp page where the map is created or on the mappress settings page.
Would like to use my own. Can you check it out?
Thanks.
Doug