If you love that wallpaper, use it in bathroom. Not really right for behind bed. I would go a drum style chandelier. In a silk pale gold. Your bed looks zen or Asian to me. I love it. But, you don't. Need to much with it. Keep it simple a more formal drape on windows, color would depend on wall color and bedding. I'm thinking a dramatic peacock satin. Use a lighter same tone on walls a rich teal. Ceiling can be gold leaf. With alight that cast shadows on ceiling at night. Then your wall paper will tie in. Furn should be mirrored.

I like the idea of bringing some black into your room. I think lamps with black shades would look very nice and because you love pink you could get black chairs with pink cushions. You need to tie in the pink in other areas of your livingroom but I would not overdue it. It's a beautiful shade of pink but too much of it would be too overpowering in my opinion. Post some more pictures of your room if you can.

There are so many wall colours that would work with your neutral furniture, that the first thing to do would be to consider what colours you might want to use in the rooms. Look for inspiration pictures and create an idea book, then use what you like to help you choose rugs, drapes and bedding before choosing the paint colour. Do you have any existing art that you want to use? That could give you clues for fabric colours and style. I wouldn't use the same colour scheme for the two bedrooms, exactly, although I might try to make them look similar by using some colours in common and keeping them in the same style. On the other hand, if you have a child who has strong ideas I'd say let him or her have considerable say in the matter for that bedroom (just this side of reason).

You can work with your currant wall color or go more yellow - that is up to you. If you do decide to go more yellow. get some small inexpensive sample bottles at the paint store, paint some poster board and hang it on a wall for couple of days because getting the right buttery yellow can be hard. A soft yellow and lavender is pretty together but I also like the sea green. When you said a combo of modern and cottage - that made me think of beach cottages, which often have soft colors (including sea green) and unfussy, calm interiors. You can put a large painting up if you have the wall space for it. Many bedrooms have tall chest, dresser mirror, tall headboard and big TV, all which take up wall space. If you can hang the painting without it being crowded by any of the things I mentioned, it should look very nice. If you wish to do a curtain fabric treatment to a wall and you have the vision of what you want - then go for it. I had a friend who did that in collage - only problem was the yards and yards of fabric needed got rather expensive. So, I would start with finding bedding you love. Simple white is good, and not too expensive. However, you might find something else light that you love, or a quilt or throw for the bottom of the bed and the colors and shades might lead you in a different direction for wall color or accents. So bedding first, then curtains, then see how your wall color is and then add accents and art - although your painting can also be an inspiration for colors.