Hi JKS
Welcome to Roots Chat.
There is not a prescribed section where you can ask for photos of graves. You may do better to amend this post title to COMPLETED then re post your request on the general Oxfordshire board again.
Perhaps your title over there could be something like; Request for a photograph of a grave - Charlton on Otmoor.
Then you need to enter the details of what you are after in the text body.
But if you do not know for sure that the grave is there and where it is then you first need to seek confirmation that the burial took place and where the grave may be in the grave yard.
Then having secured that info and posting it on here you may find someone who lives near by or passing by will take a photo and get it to you.
Hope this helps a little bit
NDRFT