Catrancher, you have taken a most beautiful photograph, and I think it's a great subject for an art quilt. I've never made an art quilt, but I think the suggestions you have received are right on the money. And I can see that you and I are much alike: we try to be too literal (grass fabric for the grass, stone fabric for stone). I probably would have done the exact same thing.
If it were me, I would finish the quilt, and consider it a learning project. Look how much you have learned all ready! Make a few more after this, then come back and reinterpret this stunning picture. I guarantee you will amaze yourself the second time around.
Good luck, and try to remember that art is a process, and a true artist is learning and growing all the time. And do show us the finished project!!