hi
I don't think the Arduino is the thing to use for controlling images.. its throughput is 115Kbaud, sure, but you can only store a few KB at a time. If the camera module connects directly to the GSM module, that would be OK, with the Arduino just issuing control signals. Otherwise I would look for another platform... but maybe some of the engineering types in here have better advice.
What might be much smarter, design-wise, faster, and a lot cheaper, is to just remote control a camera phone using the Arduino's serial port, connected to the cell phone's serial port. I say that because the camera/gsm/ connections will cost you very little as they have already been engineered and mass-manufactured. It can be done, although I have not seen any details on anyone having done it.
D
PS: even sneakier approach: use the ArduinoBT to talk to a Bluetooth enabled phone with camera, telling it when to take pics and when to send them. No hardware development! Just a lot of software.