Redoing my crusty pink room...

The color scheme you've selected sounds very nice. Since the floor is already sage, I suggest not too much sage on the walls, otherwise you'll look like you're living in a green box.

Since there's a chair rail, you can use that as a dividing point or as an accent. How about sage on the rail, with lilac both above and below it, but either the upper or lower part sponged, with the other half painted normally (flatly)? This will add interest and cover your color scheme.