Bright red is going to be so fun in there! Do you need privacy from the window? That would be one place to start with something more exciting on the window...colorful Roman shade maybe? something only on the bottom half of the window if you need privacy, so you can still get some light coming in?
Gray sounds a little...boring? I'd be tempted to look at wallpaper for that big wall; since you're going bold anyway, it could make a wonderful statement in there with the red. Hard to make suggestions without knowing your style. Some of these are pretty out there, but, hey, you're doing a red W/D so who knows what you'd like!

Or maybe just a very large piece of art?