Was the picture taken in the morning? There are always a good handful of dead bees on the patio around my hives in the morning, but by the end of the day the hives have tidied them away nicely, I put is down to bees dying tidily during the night. My mentor was surprised to start with the thought that as his hives where sounded by grass he wouldn't be able to tell if it was normal or not and that I shouldn't worry.
Ed.