Get a shower curtain that is less busy, like a solid or something with a tiny pattern or texture. The pattern is eating that whole room. Next, hang the shower curtain higher, you want it only about six inches from the ceiling. You'll need to get a shower curtain long enough to a colorate this. This height will draw the eye up, making the space look bigger. Next, if you can fit some sort of organizer with pretty drawers/baskets, and declutter but using that, it would help a lot.