Ouch, that one might be a problem, MIGHT! I'd love to test though, I'm such a sucker for tilesets, and yeah, you're evil for making it space themed

I'm usually available from 11pm - 4am during the week, nad practically any time during weekends (GMT). Yeah, I have the weirdest schedule, especially since I actually live in GMT, but that timeline should be a bonus for americans

Anyways, just looking at your requirement list, I must:
1. I've made 100+ levels, 50+ tilesets and have done numerous beta tests
2. The sooner I get the set the sooner we can get this done
3. Nice, I like people that want complete honesty, nothing is better than a good bashing during a beta test
4. Depends when you're online, above is the times I'm online, work it out

In return, you will:
1. Nothing, really, It's just a beta test, spend more time on tweaking the tileset