1. Careful art placement.
I suspect we've all been in a home with high ceilings and seen the random piece of art floating up high all by itself. I usually err on the "less is more side". However, if there is a need for art, and often there is, I would recommend something like this vertical grouping that runs from floor to ceiling (almost). The visual impact of a grouping is much better than one piece floating all alone, way up high. There really is strength in numbers.
2. Think horizontally.
The image below is a good example of minimal decor with lots of texture. The horizontal planking brings down the visual height and leaves little need for art on the walls.
I'll be honest. I've never been a fan of the focal (please don't hate), but I do see the need (or appropriate place) for one from time to time. This is the perfect example of a well placed focal wall. In the absence of window treatments, the contrasting color behind the mantel gives this room the visual punch it needs.
Window treatments can be very challenging in two story living rooms. You have two options. Either ignore them or embrace them. If you plan to ignore them and only place curtains on the lower windows, I like the idea of adding detail between the top and bottom windows as shown below.
5. Hang em high.
Nothing makes a statement like hanging curtains high in a two story living room! This can be a real stunner if custom drapery is in the budget. I love Lori's design here.
6. Add molding.
Another solution is to add molding (and in this case planking) to break up the wall.
7. Add molding and color.
The addition of the contrasting color at the top of this room creates a cozy feel down below.
I'm curious, is there anything you would add to this?