Even if you had model releases (which you'd need for commercial licensing) you'd have to clean the images of logos and other protected property (the Ford logo and the computer screen in the shot inside a vehicle, for example). Do you understand the difference between licensing for editorial use only (such as newspapers and magazines) and commercial - ads, web site banners, brochures, etc.? There's more money to be made (generally) for commercial licensing but you'd lose some of the authenticity of your shots by scrubbing them of all the prohibited stuff.

When you say you have had issues, the stock sites give rejection reasons - what reasons were you getting? And was it with getting accepted as a contributor or getting images approved for sale after acceptance as a contributor? Generally keywording has nothing to do with getting accepted as a contributor, but is critical in getting your images found by buyers.