Thank you for asking me.
Placing of Buddha images and pictures were introduced by the followers long after the Buddha passed away. It was natural therefore, to place the object of veneration at the most respected position. As with all cultures, the most honourable position would be the centre at an elevated position. On the opposing end, it would be disrespectful to haphazardly place objects of veneration anywhere we like. I would say we just need some common sense to know which position is respectful and which is not. So long as you feel right, then there is nothing to say that you are wrong. Do it with a clear conscience and all will be well. If you want my direct comment, you need to tell me how you position the photos.