@Heelix
Thanks for reply, I looked at CGT again but I found only 360 degree sky textures & partial sky images:(

..but I had a lucky turn yesterday & found almost a satisfactory solution that combines two skycube+6 images & a rotating sphere. For preliminary testing I used Boulder_bay+6.tga: the thing is to cut out the sky, replace it with a nice mat coloring & add a sphere with clouds:)

Here is my quick test app, files need more work & a better sky cube image with better sky cutout but the main concept is there:
http://www.4shared.com/get/rVnf6QbK/SkyTest.html



If someone has a better idea on how to do sky(background) or a way to enhance this concept I am open for suggestions:)