This is the documentation for ConfiForms Server/Data Center app
However, this might also work for ConfiForms cloud and in most cases it does. But please see this page to understand the differences between server and cloud versions of the ConfiForms app.
Here is an example of a form with custom field of rating points replaced by star image.
So, we have a form with one radio button field which values are replaced with star image.
Raw strorage format of an example, which demonstrates this form with script
