To take pictures with multiple cars, you need to save the replay of a race, then review it in 'Replay Theatre'. While you are viewing the race again, you can then press select to take photo's, just like normal photomode. 👍
This has been covered before but can be a tricky one to find.
Simply save a replay from a race and then go and play it back in the Replay Theatre, you will find that you are then able to take photos (in exactly the same way as in Photo drive).
There you go multiple cars in one shot, just like this
Regards
Scaff
BTW - Click on the links in my sig for more of my GT4 & TT photos.