If you check out my website, DaBronxTrafficLawyer.com, you'll see that I don't take myself too seriously and try to relay a fun quirky image to customers-- it is just a traffic ticket, you are not on death row. I relay this relaxed feeling even in my website name from the play on "The Bronx" being changed to "Da Bronx" which is how Bronx locals accent the name. Most traffic lawyers have intimidating police officers with dark shades, or a stop sign, red light, cars, or scale of justice symbol-- my old image/logo has a plump overweight cop stopping you. My preference is toward funny imagery.
New Notes added 3/17/14: Clarification on what I do. I get hired mostly by people (80%) who are driving too fast and get speeding tickets. Also represent other motorists who get moving violations in other miscellaneous categories (20%) such as running a red light, fail to stop at stop sign, no left turn sign.
Someone submitted an entry with theme of "parking meter" and was eliminated since this has nothing to do with my business.
Any creative use of symbols related to driving can be used in logo: speeding ticket sign (sample added as attached file), stop sign, traffic light symbol; a police officer, stop sign, a car, a gavel to represent the law.
I personally don't like use of symbol of scales of justice because a million other lawyers use it.
Added sample tickets I fight. Vast majority are yellow in color, a few a pink in color as shown in pdf below.