Hi Jess! Do you have a picture of the couch? yellow and gray work so well together. maybe all you need is a few pillows and a rug to pull it off?

Have you considered a slipcover for your couch, as you mentioned it was old - then you wouldn't be restricted when selecting your rug and drapery. In regards to a rug, it really depends on your taste but overdyed is a great choice for kids. When draperies match the wall, it's an easy/elegant choice. It's really hard to suggest a "look" without knowing your style, what your furniture looks like, etc. If it were me, I'd start looking at rooms that you love/could work for you and save them. You'll start to get a handle on the direction you want to go. A nice combination is grey/cream/yellow/black with cream drapery/wall color. Mixed pillow colors and a rug that brings the room together.