If you go with the black bed, get a rustic and in fall colors night stand, that will stand up with the orange. Or that particular bedspread has golds, browns, and other shades... you might even be able to work a fall leaf red (sort of a dark faded red) in there for the night stand and the red into more accent pillows that would take the Halloween away. Stay away from bright limey greens and not picking up more of the orange or black and you could make it work well.

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.

The room has exquisite bones: the windows, flooring and decorative crown molding. If simplicity is what you want but with a bit more personal taste, I suggest the following: 1) paint the walls white that has a soft, warm undertone such as Benjamin and Moore's moonlight white or Dove. (Or try any good paint store for help on picking the right white color.) Paint the molding a stark white with an egg shell or gloss finish. 2) keep the bed covering as is. I love the warm colors and mixed patterns. If you do want more comfort, yes add a thicker mattress. Can you get a fabric similar for the table top? Or just remove the fabric from the table top, painting or stenciling it with a similar pattern. (see #5 below for where to look for stencils.) 3) Move the table to the head of the bed, add a modern lamp and lots of books or other meaningful, personal items. 4) Add a comfy chair or as suggested above, pile lush floor pillows where the table is, under the window. Use complementing or solid color fabric on the floor pillows or chair. Add a small table with more lighting. (See my most popular post on Floor Pillows. Towards the end you will see examples of suitable floor pillows. Or just do a search here on Houzz and the internet.) 5) Make a dramatic statement above the bed with a very large painting. Select with care based upon your personal taste: abstract, minimal but with a hint or some of the colors found in the bedding fabric. It doesn't have to be centered, a little off centered will do since there appears to already be something on the wall above the bed. Do add a soft art lamp above the painting. (If you don't have money for the painting, purchase a very large canvas, take your time and create it yourself (collage it, play around with paint on paper before adding it to your canvas, stencil it, etc.--but have fun and make it personal) Here's a great place for getting a wide range of designs for stenciling: Cutting Edge Stencils. Note you don't have to take the design all the way to the edge of the canvas! 6) Add a small (wool) flokati rug in front of the bed. Get the kind that comes from Greece, it has long-fibers and a plush pile. These rugs are to die for when it comes to comfort and texture--and they're inexpensive. Take a look and if you like it, be sure to get wool: Flokati Rug.Net. These ideas will give you lots of varying textures to get rid of the boredom; contrasting colors for depth and drama; play up the wonderful architectural elements already found in the room; personalize it with what you love; and still, keep it simple and beautiful. Use soft lighting. Good luck!

Here are some photos that may help you. You have the ceiling height to have a nice heavy rod just above the top of you window that could run the ceiling width. That will give you the space to draw curtains back to expose the entire window. I highly suggest that you work with a designer. A good designer has access to literally thousands of fabric choices and will be able to help you in selecting the perfect fabric and design for your room.