Crisper pack for high brightness (like above shots) and now for all settings, new version does not darken and adds some contrast even at Default settings- includes textures, and skins for all.

Default settings below Stock vs Crisper (click for full size image)

to remove just delete the following folders in the "Arena" directory -Textures, Vehicles, Models, Gfx and Players and you'll be back to stock.