If you use all 12, I'd list as follows:
1) dragon
2) horse
3) tiger
4) dog
5) ox
6-12) all the rest with a marginal if any difference between any of them
The real money will be the odd sized mouse and ox as new people looking to collect can't find them. Even the 1/2 and 2oz tigers and the 5 and 10 oz rabbits should draw serious consideration down the road. The real winners will end up being the 1/2, 2, 5 and 10oz mouse and ox in my opinion. Those size dragons, snake and the rest if they ramp it up like they are currently could be ok, but not the returns like the mouse and ox. Then again, if general interest wanes, everything could be a massive money pit.