I've used zein's lab because I couldn't find any other good lab tiles when I looked around at deviantart. Thanks anyways. :)
Well, good luck scripting it! ;)
With my last hack I released an alpha that was one GYM long, and had a big event involving team rocket in it. :) I think if you want to release a small alpha that gives everyone a taste of your hack, I think you could make it one GYM, but with a big event in it too. If you want a bigger release, 2 GYMs, maybe? It's really up to you.