JPEG would be the most appropriate format.
GIF is a highly compressed image format that can only show 256 colors, so it is not photorealistic.
CMYK is a color scheme, it's not an image format.
BMP (Bitmap) is an uncompressed image format that is not very efficient.
JPEG is a lossy image compression format that is generally appropriate for reproduction. Most digital cameras, for example, shoot in the JPEG format.