Okay, well after spending a couple days on Threadless, browsing submissions and reading comments, I have decided to compile a list of design choices that will equal instant suicide for any shirt, for all you would be designers. I'm serious, stay away from this shit. These people are tough.

1. Robots. I don't know if people are just afraid of losing their jobs to robots or what, but they fucking hate these things.
2. Drips. Nobody likes a mess, now.
3. Splatter. A splatter, being even messier than a drip, is definitely not a good idea. Even if it looks cool, you're going to get panned for this.
4. Khaki. Don't put shirts on khaki. I know, it might look fine, but that doesn't matter. There are just too damned many khaki shirts out there! Also don't go with orange, but that's just because it hurts my eyes.
5. Hearts. Nobody has any love for love anymore, so don't try it.
6. Butterflies. Fuck these things and their 3 month life span!
7. Text is generally frowned upon, but that's probably because text generally doesn't look that good.
8. Placing a graphic so it will lie either on or below a girl's breasts. Every girl will hate this, so don't even risk it by putting the graphic as far away from breasts as possible. Maybe don't even put it on a t-shirt, hide it away somewhere safe from breasts.
9. Meat, cows, anything like that will be extremely offensive to the overly sensitive vegetarians.
10. Cigarettes, cigars, smoke of any sort will be extremely offensive to the overly sensitive nonsmokers.
11. Designs in general will be extremely offensive to the overly sensitive nondesigners.

I think that pretty much covers it, but there might be more. Be careful out there.