"To illustrate the theme" means to provide examples or visual representations that help explain or demonstrate the main idea or message being discussed or portrayed. Full definition
It moves into slow motion and holds on her expression of persistence, visually illustrating the theme of fighting against those who hold you back. (nextprojection.com)
Results illustrate themes for effective workplace stress management programs. (content.iospress.com)
You can upload posts along with pictures that illustrate the theme of your posts. (transparency.kununu.com)