Sauerbraten skyboxes externally edited?
- no, they're mix of cloudlayer and cloudbox, with images/textures that are already in sauerbraten.

Can my friends see these "skies" without downloading anything?
- yes, it's just mapvars, your friends can see without problems (/sendmap is necessary)

What are these jpg images on the file?
- the thumbnails that appear in the menu

Installation
customskies folder inside your sauerbraten/packages.
customskies.cfg file in the home of your sauerbraten.
Then add exec customskies.cfg in your autoexec.cfg.

Currently there are 17 "skies", if you have any contributions, send it to me.

have fun :D

images:

this is just a preview, download the zip below.

//customskies gui menu by Salatiel
customskies = [showgui customskies]
newgui "customskies" [
	guilist [
        guistayopen [
            guilist [ gencustomskyitems $_customskies1 ]
            guilist [ gencustomskyitems $_customskies2 ]
            showcustomskyshot
        ]
    ]
guitab "^f7Edit"
]"^f7CustomSkies"

//Skies names
_customskies1 = [
newmap
solarbase
moonbase
marsbase
oceanbase
lavabase
snowclear
egyptsand
plasmastorm
worldstation
]

_customskies2 = [
mothership
radiationworld
pokeball
bluehole
milkspace
hurricanered
matrixillusion
]

//Mouse over and button.	
gencustomskyitems = [
    looplist custcursky $arg1 [
        guibutton $custcursky (concatword "exec " "packages/customskies/" $custcursky ".csky")
    ]
]

//Miniatures
alias showcustomskyshot [ guibar; guiimage (concatword "packages/customskies/thumbs/" (if (> $numargs 0) [result $arg1] [result (at $guirollovername 0)]) ".jpg") $guirolloveraction 4 1 "data/cube.png"]