It was good to see some familiar faces yesterday... and some new ones.
It was great to see someone using custom maps in Tableau. I believe it was Trevor? that mentioned they had a WMS (Web Map Service) running that allowed their custom mapping/backgrounds. If you are not as fortunate to have access to one you can try out these MapBox instruction to create your own (for the adventurous): Fast and Fabulous Custom Maps using Mapbox in Tableau | DataBlick