I was wondering how to go about pencilling or shading eyebrows so that they look more uniform.
This is what I have to work with:
http://i42.tinypic.com/1247hh2.jpg

Your eyebrows look just fine to me. They don't appear to be sparse in some areas so I don't know if using an eyebrow pencil would help.

But they are not the shape that I want...

Why would you want to change your eyebrows? They look very nice.

I think they have a good shape but hey, they're YOUR brows! I use the Bare Minerals makeup line. They have an eyebrow product that's a powder (all they're products are powder). But it's really great for filling in and you apply it with a specific brush for eyebrows. It's the best thing I've ever used and looks a lot more natural than a pencil. As for shaping, that's a matter of personal preference. I choose to tweeze for my best shape but some prefer waxing or threading. You can achieve a good shape with any of these methods. You may have to let them "grow out" and start over... Hope this helps!