Civservers, and Civclassic in particular, have a long-standing tradition of in-game map art. These are made by placing blocks (usually stone reinforced at skylimit) in 128 by 128 squares aligned with the grid, using different blocks to achieve different colours on in-game map items. There are many advanced techniques associated with map art making such as "dithering" to achieve the impression of a shade not available with only the base map colours, and the use of the Schematica clientside mod to project a blueprint over the world, reducing placement mistakes and speeding up construction. As a map only takes a "snapshot" of a 128 by 128 square and does not update it automatically, the same base template can be used to create multiple map art. Some map art, however, is left completed as a monument, especially because it will then be visible when the data on sites such as http://ccmap.github.io are updated.
Map Art on Civclassic
Civclassic has numerous examples of map art; nations such as Yoahtl, Mount Augusta, and Tvtopia in particular have produced large amounts, with Tvtopia having eight full 128 by 128 squares of map art over the Sea of Tranquility (situated between Tengoku and Roe Island, Gensokyo).