This is a list of skies available in the Steam caches, along with pictures of each skybox. The light_environment settings listed (Ideal Sun Angle, Ideal Brightness, etc) are suggestions based on settings used in official maps; other values may also be appropriate. To test skies in singleplayer without recompiling the map, bring up the console and enter sv_skyname <sky_name>. Quicksave the game, load it again and the old skybox should be temporarily replaced with the new one.
|Half-Life Source Sky List|
|Source Materials Sky List|
|Lost Coast Sky List|
|Half-Life 2: Episode One Sky List|
|Half-Life 2: Episode Two Sky List|
|Team Fortress 2 Sky List|
|Left 4 Dead Sky List|
|Counter-Strike: Source Sky List|
|Day of Defeat: Source Sky List|
Full Sky List
These skies are HDR capable if mapping for games that support it.