IMHO, if you're worried about tiny details, which I'm sure you are - I'd put the same shoe tree in both shoes. I am assuming you don't have a match, otherwise you would have done this already, but it can be distracting to the eye and takes away from the cohesiveness of the photo. It's one of those things that might subconsciously affect a potential buyer without them even knowing it.
Agreed, just don't have two that are the same that size 13D, bigger then my biggest tree's. The ones in 'fit' but dont really apply any pressure.
That said here are all the photos of this pair if anyone cares. I have gotten into a routine for photos of shoes recently. Missed one shot with the shoes pointing away to the upper left.
Warning: Spoiler! (Click to show)