Change google map to custom google map (custom image) on Wordpress site

We currently have a new site, and we need the Google map with the directory listings to have a custom background. This will still be a google map with the locations plotted, etc but we would like an image of our own map to be used instead of the Google Map image. Here is the current map: [login to view URL] and here is the island image we want used instead (minus the ads, etc. Please just use the island map) [login to view URL]