You have done a beautiful job of tucking plants into the crevices of your retaining walls. Your house trim color is perfect -- just slightly lighter in hue than the retaining wall blocks. First I would paint the big, flat gray wall slightly lighter than the blocks and slightly darker than the house trim. The concrete walk and stairs I would stain a mottled blend of the blocks and the house trim colors. Next would be to paint the railing black or the house body color. Now, think of the following as creating a light, airy trellise structure from the walk-level face of the (currently gray) wall to about 7' above the top of the wall (using 6x6" posts attached to the wall) with a corresponding line of posts sunk into the terrace level 2' in from the outside edge of the wall-attached posts. The inside posts would be about 6-8" higher than the outside posts. Put 4x4" wood to attach the outside line of posts to each other and do the same with the inside line of posts. Run wood pieces at the top of the two lines of posts from the inside line to the outside line at about a 45 degree angle. They would be cantilevered up at the terrace level. Across the top of the angled pieces create your top trellise boards which run parallel to the two lines of posts. OK. There you have your basic structure. You might want to extend the structure around to follow the street side of the terrace. You could then follow the suggestion of reom10 above about creating a bench-planter on the terrace side. Your spacing of the boards parallel to the gray wall and attached to the outside posts would determine how private you wanted your terrace to be. You might want to soften the terrace "floor" by using something irregular like flagstone with groundcover plantings between the stones. From the latticework on top of your structure you could hang seasonal flower baskets. Plant vines to go up the trellis and spill down the wall. How about planting a row of tall, narrow shrubs along the neighbor's fence above your terrace to help add to your privacy and make your yard feel less 'structured'? Or, how about patio table/s with umbrellas to block your neighbor's view? Anyway, you have a fun project ahead of you.

Thanks for posting new views of your room. You are right, nothing can go in front of the paneling, and we won't block the built-in cubby. In that case let's work with the rest of the space. I found a picture on Houzz for your gallery wall. I think this will allow you to bring in color and texture and interest to your wall without taking up space like furniture would. Try to play with portraits and a couple of paintings in there too - mix it up. Otherwise I would not put anything at the top of that landing (I'd remove that console table). That picture wall should be enough visual interest to your space and it'll draw the eye to the furthest wall as you walk in your house. I would try a small piece with closed storage between the bottom steps and that door by the entry. It looks like the space is no wider than 26", so it'll be a challenge to find something that fits and is tall enough. I would not use the wooden piece you showed above because you want wider proportions and fairly narrow depth so you don't bump into it as you walk by. (something like this ) I would hang a mirror on top of primping. By the cubby you could add a single seat stool. I'm not particularly suggesting these colors for the stool and bombe chest but something along these shapes. At this point if you do that big picture wall and add these two pieces of furniture and a mirror, you might not need to hang anything on the wall above the cubby. Also, I noticed your chandelier is quite substantial for the space and hanging pretty low. Would raising it a little or replacing it by something a little smaller be an option?

What is the rest of the house like? Would you like overflow sleeping areas or more storage? If you can't raise the floor (and the ceiling?) you might consider building in some comfortable seating/storage areas that use pillows/cushions and play up the multi-level idea and make it look intentional. Similar in concept to the stepped couch.

There are some great comment here, but my take on this would be if you are going custom to take your time and look around. Many designers offer different takes on each person's preference. The colours you have are good but I'd personally would opt for a more warmer cream, with a self print pattern. I would also suggest pinch pleated curtains and not pencil pleat as you have currently, pinch pleated curtains will give you uniformed pleats from top to bottom. In addition to this I would suggest you use blackout linen to prevent light to enter the room, and possibly interlining so that you retain some thermal properties in your fixtures. Having custom made curtains are a lifetime choice for most customers, take your time and don't settle for the first company you come across. The space above your bed i would possibly add a sheer fabric roman blind which is slightly see through but enough to give you privacy if you bedroom is situated on the ground floor. You can also get the a roman blind to match your new curtains if you'd like a more repetitive theme in your bedroom. I would suggest if you do opt for a roman blind, and you are looking for a good qualities add blackout linen. If you would like a rough estimation on what you would be looking at we can assist you so you are aware of what most reputable curtain making specialist charge in this current market.