One of the reasons to use Leaflet as your JavaScript mapping API is the large number of basemaps available.
This includes very useful basemaps, showing streets, topography, cities, borders, aerial imagery, etc. that you can overlay your data on.
There are also a number of fun and artistic basemaps available, such as the heavy metal themed Spinal Map, artistic water color maps, old-timey pioneer themed maps, and others.
You can see a live version of about 20 of these basemaps at https://millermountain.com/basemap/.
Learn how to use all of these and more in your leaflet maps by watching this video.
This video is lesson #24 of approximately 65 from a course on Leaflet programming that will be available June 15, 2017. Information on that course will be available at the end of the video.
Enjoy!