They also released some 640x480 screenshots. They are included in Romero's post (fourth row), but that may not be obvious due to scaling. See the originals at http://doomgate.gamers.org/games/quake/screens.html

Fun thing about QTest1: even though you could only explore a static level and there were no creatures in it, the (then) Doom editing community had a ball delving into the details of the WAD format containing all its data. Finally they were rewarded: id had just dumped their graphics assets into the wad, and there were models inside, including the dragon, seen in the screenshots but, alas, not in the final game.