I really like this piece, the mood and atmosphere is great. It is very sense and one can quite imagine being there. The colours are nice and subtle, too. I have only two minor problems with it...when I looked at the first time I sort of had the impression that the bright part is coming out at me, rather than being further back and behind these midground cliffs. I am not entiiirely sure though what causes this. Maybe the fact, that towards the bottom the space becomes a bit less defined...but maybe that's also just me
And secondly the water on the right is drawing my eyes quite a bit towards it...I think it's a tad too dark and too equal in value throughout. There should probably be a value change in the part that is further away.
Oh and one more thing I just noticed, that's throwing me off a bit, is the sand texture on the left...it is at such a steep angle that it looks almost like a small sand hill....but neither shape nor value really reflect that, and the people sit there like on a fairly even piece of ground...so maybe I'd make the texture more horizontal.
But yeah, all that nitpicking aside, cool stuff! As I said, the mood is definitely killer!