As announced this past weekend, Wikidata is now 5 years old, congrats! 
In that announcement I discovered something I hadn't know about before —
that you can now add a small script to your account's common.js file on
to add a map to items that have coordinates. W00t!
It was created by User:Aude and it adds an interactive map when you look at
items that have coordinates. It's simple to use, just log into (or create
an account) on wikidata.org
, surf to your common.js and add in this
detailed script.  I created a snapshot of what it looks like and
uploaded it to Commons. 
There is another similar script that User:Mxn created that is very similar
but uses Overpass to generate the map. 
Enjoy using maps in Wikidata!
Product Manager, Discovery