I've linked ours. The ceiling is 18' and drops to 12 into the adjacent Living and Dining rooms. We used the accent color in the Entry and one wall in the Living Room, then dropped a couple shades. You can see the effect in room photos linked from "My Page". Here is a link that might be useful: Entry Foyer

I'm biased because I have a large round rug in the back of the LR, so I like the one you have in the foyer. It's different. I think the size is fine because you don't want to hide the wood floor completely with a larger, square rug. I like your table runner. ;)

I used Teresa's Green in a hallway that leads from the garage to the mudroom bathroom and laundry room. It's a narrow hallway with virtually no natural light, a 10' ceiling, and a built in desk and cupboard area. I gave it a multi-colored crystal fruit chandelier for interest, but the built in light over the desk area is fluorescent and the hue gets a bit sickish under that light. At some point, I will have a back splash (been saving broken pieces of china for a mosaic) there, so I'm just ignoring that small area over the desk for now. So, yes, I think it could be a great color for your purposes. I used Blue Ground in most of the laundry room, which has drab northern light, shaded by trees to boot, and needed a lot of zip, after trying 400,000,000 samples of magnificent, heart-breaking periwinkle and cornflower blues that all turned gray-green in that north-facing room.

Generally, with so much light, you could go for the darkest gray on that same color chip as one of the adjoining rooms. It would stand up to the drama of the staircase and flooring, but I think you could up the ante with a dramatic/glam chandy there too.