May I suggest a cap of your pavers on the wall and the a slightly darker gray that relates to the privacy fence beyond? That way horizontal surfaces and vertical surfaces show similarities and blends/blurs the separations?

As the appearance of the garden has a modernist style with the straight lines and concrete furniture how about a Mondrian influence and add a bold strip of blue? It is a pond and with the right shade it could look really relaxed and contemporary. My daughter's suggestion is a chalky lilac!

I would go with a gold or yellow ... of course I happen to love teal/ turquoise and gold/ yellow together. Something in variations on the photos below... maybe some pink accents if you have a girl or lime green or blue accents if you have a boy.

Accessible Beige by Benjamin Moore would be a good beige as it has a slightly pink undertone that would pick up the color in your pillows. I wouldn't go a light blue, as that seems more in keeping with bedrooms, IMO.