For the fireplace inserts go ahead and do the green order a second set of panels that you store that are more neutral. In 10 years or five years you may not like the green anymore. It's possible you won't have access to different colored panels at that time. As for the color I like the ideas of going into those silvers it would coordinate very well with your blue couch and it will pull the blues out of the curtain panels. For the wall coloring use the warm golden color in the drape. There is one piece of the flower that has this color and it will balance the weight of a dark couch. If your room is small don't go too dark in this color. You could use it on the main wall and pick two shades lighter on the other three walls.

Now for Mr 16 months... I really can't decide. His room is going to be on the cold side of the house, with not so much sun so I want it to get that cozy sort of feeling when you come into it. I was thinking yellow or orange curtains? But then I don't know what colour to do the walls. These are some fabrics I like:

It looks like you have wallpaper on the wall behind the sofa. am I right? How many walls are you painting? Post more pictures of the space if you can. My inclination would be to go deeper like BM normandy, black pepper, taos taupe, iron mountain… but hard to say with seeing so little of the actual space.

OK - I'm a beginner here on Houzz so my opinion isn't worth a lot but here it is: the room is a bit bland and lacking in character. I think you have to find some pieces you really love to bring it alive. All the suggestions are good for widening your horizons, but ultimately, you need to find things that matter to you, because it's your home and not a magazine photoshoot. That said, if it were me, I'd throw a couple of small, colorful rugs down, and put either one large painting or three smaller ones over the bed - not in a line but at different heights - to break up the binary look. I'd also put something on the wall above the heater. Then, play around with a few cushions and maybe a quilt that picks up some of the colours in your artwork.