From Pottery Barn's site, here is the Peyton drape in Oatmeal. Personally, I much prefer the sectional in Pewter. It's beautiful! You can order swatches from Room and Board, and I would highly recommend that before you purchase. I was surprised at the color variations that didn't show up on my monitor when I received swatches from Room and Board. If you need more opinions, take a picture of the swatch with the curtains and the wall color. Also, keep in mind that it's cheaper to replace paint and curtains than a sectional. So if you prefer the Pewter, I'd be more likely to purchase that and change the paint and even the drapes if necessary.

Personally, I like it the way it is -- a nice light beige. If you want to switch to gray, make sure it goes with your cabinets, flooring, and countertops (paint a large swatch on cardboard and hold it up to all those surfaces). I am not a fan of the darker accents, and I also think both of your paint options are a bit dark.

Without seeing the floors, it’s very hard to say, but somewhere in this post you can see my wood look tiles in my bathroom which are gray and it looks awesome. I would recommend getting a sample and putting it up in the basement. Since I assume there is very little natural light, the tone will largely depend on your lighting. If your flooring has a warm gray tone to it, it will probably look great. If it has a bluish cool gray tone to it, you’d have to see how it looks side by side. Hope this helps a little! Can’t believe this post is still going strong after so many years 😆

I really don't think it looks very grey in person. It is definitely a brown based color. My DD has almost her entire house BB and we have a lot. We are all anti-grey and wouldn't be very happy with it. DD is 26, first house, just getting into decorating, she told me a few weeks ago that "it is just a really nice go with anything color". I had to chuckle inside about her saying that.