In addition to using a satellite or terrain map you can also upload your own custom image map. The image used for a custom map should be large, at least 4000px.
1. Navigate to the Collection's Map.
2. Click on the dropdown and select New Custom Map
3. Give your map a title and select between Custom Map or Georeferenced Map*
3a. After selecting Custom Map you can upload a PNG or JPG file
3b. After selecting Georeferenced Map you can upload a .geotiff file*
* Georeferencing means that the internal coordinate system of your digital map, aerial photo, or floor plan can be related to a ground system of geographic coordinates. Your georeferenced digital map or image needs to be tied to a known Earth coordinate system to allow you and your users to use GPS triggers and geofenced alerts in the app. This is something that needs to be done prior to uploading the file. There are a number of tools to do this with such as https://georeferencer.com/
4. After your image has been uploaded you can add your markers to the map by dragging them onto the map.
5. Once your markers are in place you can click save or add a new map layer