2 Your map should include a preview picture. This picture will be visible from the game menu and from the servers vote screen.
5 * Load your map in the game
6 * Use the command `r_letterbox -1` in the console to turn off the HUD
7 * If your map has "waypoint" entities (like CTF or CTS maps), you can hide them with `cl_hidewaypoints 1`
8 * Take a nice screenshot with F12
9 * Go to your Xonotic user directory, on the `data/screenshot` subdirectory. Your user directory location depends on your operating system, more information [here](https://xonotic.org/faq/#where-are-the-configuration-files-located).
10 * Open the screenshot with an image editor, e.g. GIMP
11 * Crop it so that it has a 4:3 ratio
12 * Scale it to 512x512 px (weird but standard)
13 * Save it as a JPG file (~90% quality)
14 * Put it in the same location as the bsp file, with the same name (see next chapter for packaging rules).
16 Original source of information: https://forums.xonotic.org/showthread.php?tid=6067&pid=75757#pid75757