ACF Google Maps - Markers
The position on the map is identified by a marker. You can choose the shape of it.
ACF FIELD Image Marker
You could use a customized ACF Image Field set to the post in addition to the GoogleMap Field.
The metabox in the management of the single post.
NOTE: If you don't pick any custom image the marker will be the default one from Google Maps.
USING DYNAMIC MARKERS
You can assign me markers dynamically on your template:
1) Click on Dynamic Tags, be sure of having the Marker > Map (ACF) option cleared.
2) Select the dynamic source you want to use for the Markers:
We used the Featured Image from the posts for this example.
3) The Featured Image inside of the post will replace the Marker:
At last the final result, the marker inside of the map, replaced by the featured image: