Doing interactive visual scales is not DirectRT's strong suit (MediaLab is better for that kind of thing), but take a look at the Modern Racism sample (in the Applications sample folder, I believe). It requires that you make the scale graphic yourself (see attached sample below) but then you can use the compound screens functionality to insert graphics (either fixed or random) at the end of each scale. Let me know if you have any trouble with it.
See also: www.empirisoft.com/directrt/help/directrt_samples_assessing_modern_racism.htm
www.empirisoft.com/directrt/help/directrt_samples_compound_screens.htm