Each GeoDirectory category has two icons. The Map Icon is the marker image used on maps. The Category Icon is a Font Awesome icon used in places like the GD > Categories block. You set both when you add or edit a category at Places > Categories.
Category Icon
Click the Category Icon field and choose an icon from the picker. The picker offers the icons of the Font Awesome version your site loads. If an icon you want is missing, go to Settings > Font Awesome, check the Version setting, then clear any cache. See Font Awesome Settings.
Set a Category Color as well. GeoDirectory uses the icon and the color when it generates a marker, as described below.
Map Icon
You do not have to upload your own markers. If you leave Map Icon empty and choose a Category Icon and Category Color, GeoDirectory generates a marker from them. To use your own image instead, click Select Icon and pick it from the media library.
Listings in a category with no marker use the Default marker icon at GeoDirectory > Settings > General, under Map Settings. It is an advanced setting, so click Show Advanced to see it.
Size and format for marker images
Use a PNG with a transparent background, around 30 to 50 pixels wide and high. Much bigger images look oversized on the map and cover nearby markers. You can make markers in any image editor or use a free marker set, as long as its license allows it. Many sites only make a marker for each parent category and give the child categories the same image.
For the other category settings, see Create a Category.