Doom 2 beta screenshots?

Just noticed this but..

I never seen the Phobos Sky Texture used in any of the current Doom 2 maps. Yet they show up in some of the screenshots around the web, including the steam store page. (Most obvious one being the one with the chaingunner in the green marble alleyway. Are these the beta shots?

Sorry if this seems trivial, but I like researching these things.

You can find a lot of interesting stuff about the D2 beta in this thread: http://www.doomworld.com/vb/doom-general/68882-doom-ii-had-a-preused-texture-doom2-beta-discussion/