You have a nice geometric, somewhat masculine look going here. I would play that up. I don't think you need to change the wall or carpet color as they seem to be a nice neutral background. Are they cream? is the purple more plum? and is the blue more of a steel blue/gray? The furniture is chocolate brown? I love the striped pillow on the chair. I would layer a wool steel blue/gray area rug and then play up the blue/plum in the pillows. A wool plaid or blue gray herringbone in a couple of throw pillows (replace a few of the solid color pillows) could help to pull it all together. Kind of like the colors in the picture of this bag. Adding brown leather cording would be a great compliment on the pillows. (Not sure the area rug in front of the TV is adding anything)

If you want to highlight the staircase wall then your could use earthy colours such as a yellow ochre! The wall could be enhanced even more by using suitable frames and making a good collage composition for all the photos that you have (I can see many lying on the dining table). This colour would match well with wooden furnitures

Well I'll try to make a 3d of the room and upload it. But that will take some time. Thank you :)

Unfortunately all your options require custom work: It looks like you need an 18" corner cabinet. You will have to modify the last wall cabinet on the left. As I am eyeballing it, you should be able to cut the last cabinet in the middle and then shorten the left section to fit the space of the wall next to the door trim. It's an option that makes the area looks symmetric. Or you can install shelves over the sink. I would not recommend it because it will take the looks away. And the last option will be to remove the last cabinet, shorten it so it fits over the sink and install a single cabinet where the double one was. This will leave a triangle space behind the corner where the two cabinets will meet. You can block the space under it. Hope this helps!