Indoor flash always produces harsh unsightly shadows on the backdrop. Could have pushed the tonal range harder at the bottom end and given its mono, could have clipped the tonal extremes to make for a more dramatic image
There's a very large shadow behind your model. Don't be afraid to move your furniture further from the wall.
There's also no true blacks or whites in the photo, which is causing it to look very flat to me. I use Curves in Photoshop to make sure I have whites and blacks set to create the best depth. With this photo I used the black eyedropper in Curves to make the blacks blacker. Doing this made your subject pop right out of the background.
The shadow cast from the flash is distracting. Also I thinks this could use a contrast increase as there is a lot of similar grey tones which should be spread more evenly across the black- white range. On the plus side it's a nice pose and composition.