Quoting JD Luse
Thanks for the comment! As for which pieces to buy for a castle, it looks like you've got it covered with all those slopes. =) Actually, I'd focus on arches, plain old bricks, and 1x1 cylinders. Just go look at any good castle and pick out the most used pieces. That's what I did.
Thanks for your help! But, what you're looking at here is all light grey. I could use none of these in a castle. That's why I'm planning on buying a bunch of light bley pieces. I only have about 20 of them.