Honestly, I don't see the need for preview images; the files are pretty small, and you can see what they look like quite easily in the map editor (or once you know the letter codes better, by just looking at the text files).
Also, I'm nowhere near half the maps yet; there's 1017 maps (including this pack) currently, and I've only done 428 maps, so Variety Pack 7 will be the half-the-maps-pack if no-one else submits a load of maps. ^^