I would never presell hatchlings because I would not want to anger the egg gods. I mean, not only is it a risk to produce any certain morphs or sexes but you can't guarantee that you'll get eggs at all.
As far as crowd-funding with t-shirts, I think you might be able to offer tshirts or stickers with actual hatchling photos on them. So someone can pick which of the hatchlings they would get on the tshirt/sticker/hat... once the eggs hatch.
Or you could presell by offering to give credit for the money they put in, with a certain amount of discount at the different levels.
So if someone pledges $100, they get $150 credit to spend with you when you have things to sell. But if they pledge $200, they get $250 credit, but ALSo a 10% discount on the price. That way people would have a reason to be paying you start-up money. Since the hatchlings don't actually cost you much, you might make out okay.
The downside to that would be if you didn't have enough hatchlings to let everyone use their pledged money or how to say what order people get to pick hatchlings in.