You can always skip ahead in your Atkin's book to the chapters on OWL and Maintenance - check the foods you add back in. You should get some ideas from that.

Foods like :

Sour apples (macs, green apples)
Grapefruit (half)
Cottage cheese
Sweet potatoes (not regular potatoes)
More veggies - extra servings of the ones you're already eating.

You can either increase your carbs slightly at each meal, for an overall increase, or you can increase them in larger amounts around your workouts - Say 15 or 20g split between pre and post workout meals as fuel for your muscles. Experimenting will give you an idea of how much you need and which method works best for you.

Try to avoid increasing with just fruits - your goal is to provide muscle glycogen, fructose replentishes liver glycogen stores and isn't a big help.

-Nat