Hey deathknife, this is a sweet plugin, I remember using one similar years ago back in 1.6 and everyone loved it.
A couple questions, does this apply your selected skybox to every map, or only for whatever map you chose a skybox on?
Also, is it possible to add a "reset sky" option back to the map default? This would be especially helpful for maps that have custom skyboxes packed in with the bsp, that wouldn't be selectable.