I used Wally to put all of the pictures into a wad so Wally generates their palettes, I then selected all of the skybox images and exported them in a group into TGA's into the gfx/env folder of my mod folder.
J.A.C.K. also gave me a similar error:
"Warning: TGAImageLoader: Only type 2 (RGB), 3 (gray), and 10 (RGB) TGA images supported"
I ignored the warning and started the game anyway after compiling the map, it defaulted to the default skybox, and gave me this error in the console:
LoadTGA: Only type 2 and 10 targa RGB images supported
R_LoadSkys: Couldn't load gfx/env/goldskyrt.tga
Does wally not support the kind of TGA's that half life needs?
all the images are also 256 by 256.