The problem with digital cameras is that they usually don't use simple serial communication. It probably uses USB, which will prove to be an issue. Sure, your arduino has an FTDI chip which converts serial to USB compatible communication, but you can't just hook up your arduino USB cable to it and expect it to work. You'll probably find quite quickly that the camera is not a "smart" device. The camera probably does not have a USB host controller.
Most "dumb" USB devices (memory sticks, headphones, keyboards, mice, etc) require a driver or a host controller in order to access the device. Windows and Mac (and even Linux most of the time) these days come standard with lots of generic drivers that can be used to access similar devices. For any extra functionality, you need a specific driver from the manufacturer.
You may be able to hack the commands to access the camera's hardware, but it probably won't be very easy. You might even be able to get a USB listner and use some Casio software to access the camera and snoop on the USB data to find out what they're sending to access the camera. That will be hard and take time... but is possible. I'm not going to spend my time doing that though... not when I can buy a cheap cmos camera that will do the trick (and is meant to work with microcontrollers) for not much more than $20-25.