[6S.Maraz]

I've compiled map_C's for my slot map using 8bit Grayscale, and it works fine.

Yes, all examples I have seen of map_C.tga are 8 bit grayscale.

See for instance Balaton, map_C.tga is 1024x5824 pixels, image size is 5824 K Bytes, i.e. i byte (8 bits) per pixel.

I think there is difference in the coastline (shallow or steep) according to the shading between black (sea) and white (ground) but I am not sure of that.

Maraz