Hmm. The rough sketch idea is good, but there's a difference between a sketchy style and messiness. Here, the white parts of her skin look clean and sharp, but the black sketchy lineart and hair clashes with that and makes it look kinda messy. I would suggest if you wanted to make the whole wall sketchy, then to make the WHOLE thing from sketchy strokes, cause if not then those parts you did make sketchy will appear messy in comparison to other clean areas. `sjade1 and `anbuu have some great sketchy styled walls you may want to take a look at to see what I mean. :)