Nice work, the sea is very convincing but I would have darkened the cliffs a bit to blend in with the grey rocks in the rest of the photo. You know, if they hadn't geiven the game away I don't think I would have realised you added it... I was assuming that you used one of the coastal starter images.
Thats too bad cos it would be definitly a contender. The castle is very well blended to the cliffs, though i think the green and orange is a little strong in places. Nonetheless a very bright vivid view of your expansive imagination. Great job!