At the moment there is no storage limit, but we may get in touch to discuss if your account gets big enough to become an issue for us. In the short term we will set a reasonable limit for uploads to make things clearer.
As we get closer to the end of our Beta phase, we will define the exact conditions for free and paid/sponsored accounts. As the infrastructure required to run Pryv isn't free, paid accounts are the only real guarantee we can offer that our goals are aligned with yours (so that you are not the product). We'll provide more information about future pricing on our website as soon as we can.