I have painted the bench part a nice blue and bowed to Anand's love of yellow, and I think I'm reasonably pleased with the result. (I'd better be -- my arm hurts, so it's not getting repainted anytime soon!) It's kid-friendly, which is obviously good for a playroom, but still just muted enough that I don't mind hanging out in the space. Esp. with the new windows, it's quite sunny and cheerful up there now -- maybe slightly less open in feel than before, with the all off-white, but more cozy and fun.
Kevin gets home tonight; we'll see what he thinks, and if he agrees that the green (sampled in third photo) would be good on the rest of the lower wall. If so, that'll hopefully get painted too in the next few days.
Paint colors: Sherwin Williams Peacock Plume and Butterfield Yellow.