A different paint color on the walls to separate the areas?

Would suggest cleaning off the ledge and doing a beautiful piece of art centered in that area. Just because you have a ledge, you don't need to fill it. Think of the ledge as a line of demarcation and a place to make a statement on the wall rather than the ledge.

Yes, I agree with Karen, paint that wall an accent color and showcase a fabulous piece of art! When I look at stuff on ledges I just think of dusting...

I'm glad you provided other pictures. The first doesn't show how tall the space is above. I agree with the others. However, I don't mind things on the ledge, what is there is just too short. For proper scale it should have larger items at different heights and artwork hung on wall as well.

I like the light fixture!

Honestly I don't think you need to put 'stuff' on the ledge, but if you do just make sure they work with the scale of the overall space.

I wouldn't paint it an accent color if you consider it awkward. It will just draw more attention to it. I have an accent ledge in my house that is painted an accent color and it just draws more attention to the area. It really doesn't need anything at all. I'd leave it bare.