Currently there's only two sensors supported via the I2C interface: the Omnivision OV5647 used in the V1 modules (5Mp maximum resolution), and the Sony IMX219 used in the V2 modules (8Mp maximum resolution).
Anything else requires raw sensor access which is a rather involved subject (as the linked thread demonstrates; I deliberately haven't included any particular details here because the amount required to be useful would be quite excessive and probably subject to change).
Secondly, on the subject of open-source camera firmware (raised in the comments): don't hold your breath. This is extremely unlikely given:
The firmware is very lucrative for Broadcom (the Pi's camera firmware is a variant of that which is used in several mobile cameras).
The firmware implements things covered by patents which require a license to distribute or use (e.g. the H.264 encoder). How it would be possible to license such things in an open firmware is likely to be a question that requires expensive lawyers to answer, and there's no obvious commercial benefit to Broadcom for doing so.
The sensors' register settings are only provided under NDA (the OmniVision set, at least, have leaked online but the firmware developers have noted even those aren't sufficient to actually get the firmware working). Hence, open sourcing the firmware likely requires persuading OmniVision and Sony to open their NDA'd datasheets to the public (or at least to relax the NDA).
The firmware is currently built on the ThreadX RTOS which has a royalty-free, but nonetheless commercial license. I've heard the VCOS layer is an abstraction which potentially means another RTOS could be used instead but that's still a non-trivial conversion (and again, there's no commercial incentive for doing this work).
In other words, it's not impossible but my understanding is that the probability is so remote (lots of work for no obvious commercial gain) there's no point holding out for such an eventuality.
Finally, I should add, for anyone reading this and getting the wrong end of the stick (as this topic comes up from time to time on the Pi forums, and is usually a source of some consternation): the Pi Foundation has no control over this, they merely license the firmware from Broadcom.