Same way you do with any BF1942 mod.
Added (2010-06-19, 9:55 PM)
New lighting for night maps:
I finally managed to make a whole new custom Pallete.pal file for the lightmaps for the statics. What I did was to create a new gradient in Gimp (free equivalent of Photoshop). I used black as the starting color and the terrain sun color as defined in the real map as the base color it uses in the gradient. So it fades from black on one side of the image to a light bluish color like the map does with the real game. I then saved that as a indexed 256 color BMP. Then used IrfanView to export the palette. The resulting pallete file is not a version compatible with the game, so I used another app called PaletteMaker to open and resave as a RIFF format Palette.
Voila! I got me some bluish tinted statics just at the level as it appears in the real game!
I then applied a 40% color tint to the leaf/undergrowth textures and a 20% tint to the detail texture to make the terrain match up with the lighting. Then applied some lighting changes to the init.con file of the map and that is the result.
Opinions? I think it looks closer to the game, but need some opinions on it as I have not made a final decision on if to include this in v1.8 on all the night maps. I also made a day map version of the palette.pal file taken from the light settings from a day map in the real game and plan to alter how the day maps are lighted too.
As far as I can tell very little to no mods actually have custom Palette files for the lightmaps. (they all just used some from exiting vanilla maps as far as I can tell)
The process to make a custom palette file is a bit complicated though as I couldn't find a app dedicated to exporting the palettes from BMP files. So I had to involve two apps plus Gimp to make a new palette file.