The gt5 photomode section of GTP is vastly more popular than the gt5 tuning, drag racing, drifting, seasonal events and racing/events sub-forums. It actually is one of the features of this site, only surpassed by the marketplace and sub-forums that are very much general.
Plus photomode embodies what the gran turismo franchise represents.
Naturally I'm all for it
To be honest, though, I don't see much that needs immediate attention; as others have said, there are other, more important aspects of the game to be worked on. GT5 already has one of the most in-depth Photomodes of any racing game, and the basics are all great. Introducing the option to have multiple cars at a shoot would be important, I'd agree, and perhaps simulating different lenses could be interesting. As much as it's currently inaccurate when it comes to F-Stops and shutter speeds (in relation to their effect on available light), I'd like the basic system to stay in place to encourage more users to take part.
Some things I miss from GT4 need to return though; when watching a replay, pausing it and entering Photomode gave us the exact same view as the replay, which sometimes made for incredible aerial shots, or otherwise impossible-to-access locations. That needs to return. As for the current approach of allowing us to wander around the track itself; great, but give us more vertical free space. I shouldn't be limited to 20-ish feet above the track.
Tying into replays just as much as Photomode; a proper fast forward and rewind feature needs to be implemented. When you're trying to capture that specific moment in a hard-fought race, it'd be incredibly helpful.
Oh, and come on PD; give us a location that's just a studio space. We know you can do it - it's in the dealership, already - so give the players access. Same with all those Prologue locations that show up in the main menu. Letting us get the camera into the car without having to resort to glitching would be handy too; if you want to brag about the amount of detail you've put into the car interiors, give players a chance to document it. Yes, they might get too close and see an ugly texture here and there; but it's no worse than what you've already put on the track in the form of the Standards!