Store Locator Plus allows you to set a custom marker for all of your locations.
Upload Your Marker
Start by uploading the marker to a web accessible location.
Go to Media / Add New in the WordPress admin panel.
Upload your marker.
View the attachment details for the newly uploaded marker and copy the URL.
Upload your map marker to a public web URL. This can be an Amazon S3 location, your web server via sFTP/FTP or cPanel, or any other location that is open to the general public where you have write privileges.
Activate The Marker
WPSLP – Go to the Store Locator Plus Settings / Map tab.
MySLP – Go to the SLP sidebar and under Settings / Map tab select the default location marker or your custom marker (available feature with the Professional level plan markers can be set individually for locations).
Enter the URL for the media file.
Save the settings.
Please note the above video shows Advance Options. That has been changed now to SLP. All location edits and changes for MYSLP should be done under the Store Locator Plus menu.