We would like to (potentially) include a tag line that says something like "Central and Western Massachusetts" or otherwise indicates our service area. We would not use the tag line with every instance of our logo, though.
Although we are are non-profit, we are essentially a law firm that represents low-income and other disenfranchised people. We want to convey a sense of professionalism so that clients and potential donors understand that just because we are "free" lawyers, we are every bit as skilled and zealous in the pursuit of justice as the most expensive law firm.
We value and respect the diverse backgrounds of our clients (age, gender, disability status, sexual orientation, "race", national origin, etc.)
Some other ideas we like include using one of the following in the image: hands of different colors, a pillar (like on the Supreme Court building), something to represent "a fresh start" or "a new and better day".