Ok so here is the hard part. What should be free and what should be premium. You want to have a good balance because having nothing available for the free players doesn't always result in people buying premium, they just stop playing.
I think that when new poses are added that the older poses should become available to the free players, but maybe at a higher XP cost like 3xs the XP and possibly cost in-money as well. This way it does not feel like it is being given away. This should also satisfy the premium users because they wont feel upset because there is still a benefit to being premium. You don't have to work as hard, everything costs less, and you get it sooner.