A) -As a general rule of thumb you would like textures to be at least twice your rendering resolution. So if your rendering at PAL resolution, you want the textures to be around twice 720x576 so around 1440x1152 should be okay… Of course it depends on how close you get to the Camera and other variables as well
If your doing HD stuff, something like 4K maps would be preferred… (4096x4096)
So you would be looking for something with a large MP factor if you can afford it…
For example 8MP Camera have around 3456 pixels wide by 2304 pixels high.
But if your budget could afford a 10-12MP Camera, than it cannot hurt…
B) - Look for manual controls, (Focus/Zoom,Exposure, etc) Look for image quality, and ergonmoics… You will want RAW support, perhaps bracketed exposure.
C) - I like Panasonic P&S Digital Camera’s they have a little noise, but they take sharp good quality images (Leica Lens), and it does me very well for textures. There are various models… Panasonic FZ50 is a 10MP camera with RAW, and decent zoom lens.
Check out www.dpreview.com, they have forums and the best reviews on the net…
Check out the models in your price range, and perhaps report back. Without a specific budget in mind it’s hard for me to reccomend something.