It's a very inexpensive investment to buy a pad of these releases and keep it in your camera bag. It's much easier to get a release signed when you take the photograph, rather than to find out at a later date that you have a sale for the photograph and can't remember who the person was or don't know how to get in touch with him. Just be sure you get a release, or don't use that particular photograph. You don't want a lawsuit on your hands for unauthorized use of a photo. That will make advertising too expensive regardless of the media you choose.
Many banks like to have displays of various types from time to time.
Photographs make a very effective display, and all the prints don't have to be tremendous color prints, either. Ask your bank about sponsoring a display of all the different types of work you do. If the bank is in a stand alone building, a Floatograph Photo will go a long way in keeping your photos' on display longer. The bank could then display these portraits in a show in the lobby before hanging them in other appropriate places. Also suggest executive portraits of the members of the bank's board of directors, which later could be hung in the board room.