Inverting the rules was really cool :)
The rules remind me a lot of Skyscraper logic puzzles: http://www.conceptispuzzles.com/index.aspx?uri=puzzle/skyscrapers
I wonder if you invert the expectations one more time and instead all the diamonds are fixed and you need to place the rocks and ravens? It would probably be too easy just like that so you might need to add a rule where no two ravens can be next to each other.