Nervous Girls

I sketched this today.  I was playing with expressions.  I wonder what they’re so nervous about.

nervous girls 500

Perception – Final Version

Okay, so does this work or not?  I was thinking perhaps it could use some more vague figures looming behind the four in the thought bubble, but I’m not sure.  I’m sending this one out for publication (I hope) and I want it as strong as possible.  Do you see anything that needs work?   Is the idea clear?