The two photos, apparently from surveillance video, show a man in a trenchcoat and hat holding a cane.
Patel was found murdered in an office building in the 1300-block of Shermer Road at about 7:30 p.m. Dec. 7.
Police released the photos on Wednesday and noted that they believe the murder was "an isolated incident and there is no threat to the community."
Friends described Patel as a strong family man who lived in Prospect Heights, 20 minutes away from his job. As a lawyer he worked on small business and real estate transactions, according to his website.
Anyone with information is asked to call Northbrook police at 847-664-4181.