Brown waste materials are a source of Carbon and you need double the carbon in your compost pile. Remember the ratio of Carbon to Nitrogen is 2:1. Here's some good sources of Carbon:

Leaves

Straw

Paper

Shredded branches, stalks, twigs and bark

Saw dust

Pine needles

Nut shells

Dryer lint

These brown waste materials can be harder to break down than the green waste materials. You can shred or cut items into smaller pieces that will help them break down faster.