Mirage has been popular as a custom map among the Counter-Strike community for years. After Global Offensive was released, Valve decided to include the map as an official bomb defusal map. As with all official maps, Valve updated the visuals and tweaked the gameplay for better competitive play. For instance, the original versions of Mirage had textures similar to Italy, but was later updated to reflect a Moroccan style.
Although Mirage was originally an unofficial map (as de_mirage, which is available since 1.6 version), it was remade by Valve, and released for Counter-Strike: Global Offensive as an official map.
The overall concept and overhaul of Mirage may have been inspired by Sandstorm as the style of the map is a mix of Dust2 and Italy.
With the exception of the Arsenal maps, Mirage was the first new map in Counter-Strike: Global Offensive, though not the first original map since it is a remade version of a custom map.
There are two TVs with SMPTE color bars in this map. If they are attacked with any weapon, the TVs will no longer function.