Although industrial-organizational psychologists who work in the business industry can focus on organizations in general, it is normal for them to only work in larger organizations. Many of the psychological issues that pertain to the job role tend to revolve around organizations that have a large, set hierarchy, and as such smaller and medium-sized businesses tend not to be a primary focus.
In the academic field, those who work as industrial-organizational psychologists can expect to work in universities and colleges. Although the field itself is specialized, academics who focus on this particular branch of psychology are just as likely to find themselves lecturing undergraduates as they are postgraduates.
Finally, industrial-organizational psychologists can work on a freelance basis. This tends to come later in their career when a lot of experience has been gained, and involves being outsourced by larger corporations.