I created a new ProjectPier theme called "kamp". Expand as the folder "kamp". Copy the "kamp" folder into public/assets/themes of ProjectPier. Go into Administration > Settings > General > Themes and select "kamp".
It looks sort of loosely like Basecamp. It was easy to build. I just popped open Firebug on Firefox, selected things, and then began editing the CSS. As I did that, I copied those changes into the project file and refreshed the page on another browser tab.
I'm still waiting on a response from the ProjectPier team to let me post on their site. You can have an early release of it here, instead.