Google has created a system to allow third parties to place data (be it an interactive map or a static image map) on Google Maps and make it accessible to a larger audience.
The project - Google Maps Gallery - enables organizations to share data on a map to be publicly discovered by people using Google Maps, Google Earth and search engines.
Google says:

"Maps Gallery works like an interactive, digital atlas. You can explore historic city plans, climate trends, housing affordability, shipwrecks and up-to-date evacuation routes.
"As the Gallery grows, it’ll be easier to find out where we’ve been, where we are, and where we’re going, giving us a new way to look at the world around us."
In the context of the travel industry, the use-cases for travel brands to leverage the power of a digital atlas is enormous.
From a PR perspective, airports for example can launch a Gallery that shows how the airport looked ten years ago, and how it has evolved (or expanded) over time.
In case of destination marketing companies or tourism organizations, they can plot all attractions available in the city/country, the most visited attractions/streets/regions, etc.
For example, when Tourism Victoria executed its Remote Control Tourist project few months ago, it mapped all restaurants, cafes, bars, parks etc in Google Maps.
Clicking on each point of interest gave more information about a venue. Tnooz asked the organization about this data effort, it said:

"As a tourism board, we have a wealth of data at our disposal and have long recognised the importance of good geographic data and photography for tourists.
"Our team manually mapped approximately 300 places around Melbourne prior to the campaign. Because we were never certain about exactly where the Remote Control Tourists would visit, we also added many more of the locations during the live activation.
"The 1,537 Instagram photos that accompany the points of interest were shot live and fed back to our control room as the Remote Control Tourists visited each location, then incorporated into the live feed in real-time and the POI on the map."
Now, projects like this can be made discoverable in Gallery via channels like Google Maps, Earth and leading search engines.
In Gallery, someone has created a map of 8,000 singers by birthplace, clicking on each map point gives details about the singer.
Now, imagine someone creating a similar map of all tours and activities service providers across the globe (along with details of each company), another map of all cruise passenger ports, and an another map that has the head quarters of all OTAs across the globe.
In the FAQ section of Map Gallery, a key clarification was provided:

"Is this the same as Google Map Maker or project Groundtruth? No, the Google Maps Gallery enables authoritative publishers to overlay their content on top of Google’s base map and make it accessible and useful. Unlike Google Map Maker or Project Groundtruth, our goal is to help public data providers distribute their content, not to incorporate that content into the base map."
Organizations can now submit their request to join the Map Gallery initiative. If you are an individual, you can submit your request - here.