Are you using the Offline Maps option? Go to Map>Background Maps>Offline.
Another option would be to use a background image. The following article goes into more detail on this:
Hope this helps!
I think you want to correctly position the image as if it were 'geo-aware?' This would mean you need to geo-register the image (so it exists on the earth, instead of an arbitrary plane), this can be done by importing the image into Google Earth and 'rubber stamping' this means you effectively zoom into the real world location of the stadium and overlay your image. Any GIS can do this for you as well. You use a number of control points to register the image to the lng/lat (ie, earth coordinates). To import into Tableau, you would need to know the extent, then can be viewed as a background image. If you don't care where on the planet the sports arena is located, please ignore!
Thanks Tracy, The offline option worked. .
From the dashboard view offline option is not enabled unless I select the geo map, but at least this got me going in the right direction.