High Resolution Background Cube

What is the preferred way to display a high resolution environment? I would like to display a high resolution (4k+ 8 bit color) on the inside of a sphere or cubemap, and would appreciate any advice on how to author the texture. I have been looking at Lys and IBLBaker, but it is not clear how to explicitly author mipmap levels for display, and any attempt to attach them to a scene so far has displayed them with much distortion.