Hi Ingo,
You might want to look at Icon Radiobutton widget https://marketplace.mendix.com/link/component/114190
Not sure if it supports your version of Mendix 8 but maybe worth a try.
It will work with 8.18.16 and for user input it fits. Is there a similar solution for existing data, for example showing an existing data set? I can define several image widgets and can control the fronted visualization by the visibility parameter. But in my case I have to define at least 15 image widgets. That sounds not very comfortable.