Augmenting an existing graph or building one from scratch?
If you are not yet familiar with BloodHound (https://github.com/BloodHoundAD), you should look at it. It's a great toolset to analyze and represent Windows infrastructure, and, behind the scenes, it also leverages a Neo4j graph database.
After importing data into the BloodHound database, you can augment existing nodes and edges with more relations and metadata, such as organization information, social networks, or cloud infrastructure. That is a quick approach to get some results beyond Windows infrastructure while still fitting into the overall model. Hence, if you already have a BloodHound-based graph database, consider that as a great starting point to map out your entire organization as much as possible.
Similarly, there is Cartography (https://github.com/lyft/cartography), which focuses more on cloud assets, but it also uses Neo4j for data storage. A nice experiment is merging two datasets into one. Both projects...