A repetitive image or idea in a text is a motif.
Explanation
A motif is an idea, element or aspect that is repeated at multiple times throughout a text to highlight the theme or message behind the text, the author is referring to.
An idea can be referred to as motif only if it used frequently.
The re-currency can also take place in various forms.
A motif provides the completed structural framework to form the theme.
Examples can be seen in Shakespeare's Romeo and Juliet- the phrase 'light and dark' is repeated in other forms like the night (moon) is no match for Juliet's beauty.