Very nice as a background, but needs a bit more of a focal point in my opinion. I find myself taking similar picutures of rocks that are pleasing to look at, but don't always work as well as a static image.
Doesn't really have anything to focus on. Perhaps two or three larger shells placed in areas to enhance composition elements would provide more interest and some contrast.
Hmmm. Some perpective might have been nice here to give the shadows more "meaning." It can be hard to capture shells on a beach in sunlight without over-exposing highly reflective shiny surfaces. There is little of that here though - well done.