No yellow (except as an accent color for some faction, perhaps).
The castle theme being one of the larger attractions for people building MOCs, I would have liked LEGO to sell gray brick packs. $0.15 for a gray 1x2 is ridiculous when you have to buy 2000 (let alone 3000 or 10000) of them.
This is one of the many cases where PAB online beats bricklink, where the cheapest NEW pieces in bulk volumes (more than 500) are twice as much as PAB (well, I limit to North America in my searches, YMMV).
So... I'd love to see "castle packs" of bricks. Of course, there's a lot of things I'd like LEGO to do.
One discussion on Eurobricks throws out the idea of modular castles with "theme" packs for different factions. I like that idea a lot. I built a modular wall for a walled city (based on the community build model)... only 16 studs wide, only about 85 pieces total, and LDD told me it would be over $35.00.
I'm running with the modular idea in "midi" scale (I guess that's an appropriate name for it) using the microfigs from Minotaurus, and I like how it's turning out.
BTW, I love those microfigures... I wish LEGO sold them separately. Yes, I know they're not pose-able and can't carry weapons, but it's better than a round 1x1 to "represent" the little guys that would be there. Can't wait to get my order from BL to have some unified colors so I can take pics and show it off. I think I may be able to convince a few naysayers of the beauty of the microfigures.