Is there a way to add extra pictures to a vehicle after the fact or do we have to reshoot the whole car?

What should I do if I forgot to shoot some features or want to add any?

If you have an automatic connexion:

If you shoot only a couple of pictures with the same VIN or Stock, all the pictures will be replaced by those ones. If you want to add those to an existing photoshoot in your inventory management system, you should enter the same VIN or Stock but add an "X" at the end so the system does not upload it to your inventory management system. 

Then you can go on your Pixel Guru dashboard, download those extra pictures and add it manually to your inventory management system.