If you want to make a wall the focus of the room, there are many ways to do so.
You can paint it a different color, although you need to balance the color with another wall as well usually.
If you are going to do drapes in lavender, that is great, how far are they away from the focal wall?
What I would suggest either way, is to take the focal wall and make it stand out one of many ways. Color, or what's on it. I have found, especially with big walls that you want to focus on, that using a painting either framed or just painted on the wall, can really make it shine. Make sure that the painting pulls all the colors in together to pull the room together. I used to sell paintings, and you can put any paintings up together that you want usually as long as they are the same colors, or pulling colors from each other and the room. You can also tell a story with the paintings. If you can find some to match a story. You can pull in much of a wall by doing this.
You could even make the paintings whimsy with the colors that you are using. I can see a white gazebo, with a woman in a dress and trees around. If you can find a painting like that, you can pull the sage from the trees, and hopefully find some lavender in there as well.
Remember, you have to like it as well.
You can find paintings at starving artist shows all over the place and they aren't very expensive at all.
As for the furniture, if you are using brown for the floor, I would suggest something to match the floor. Or something that is close but stands out on it's own as well. Make sure it has enough or not any color that if you decide in a couple of years to change the walls, that it will still match. Maybe stay with a neutral color, light brown, beige or even a green that will go with the walls.
You could even due blinds, white or creme, and use a valance in lavender at the top to bring out the colors that you want. And use a very pretty rack to hold the valance with.
Good Luck and I hope you get it all put together.