you know what I do?
i set sky color in code
i make a transparent cloudy sky tga file. the transparency allows my sky to still have the color set in the code. that way i can have my cloudy sky and change the colors dynamically in code.
on top of that i add a transparent 6 sided PNG skycube for eventual mountains. and that not only looks awesome it also is dynamically changeable and doesnt use alot of recources...