The sky appears on most maps of each game in the series.
The TimeSplitters Future Perfect Mapmaker has the following skies to choose from:
Clear Sky - A regular, normal looking daytime sky.
Abstract - Black with red background
Cold Night Sky - A regular, night sky.
Overcast - Afternoon / Evening in urban places
Sunset - A simple sunset.
Arctic - A blue sky with visible frozen mountains in the background.
Alien - An alien-looking sky with two visible planets.
Gloomy - Rainy afternoon
Cloudy - Rainy
Dusk - Afternoon / Night in desert places