You can change the title and image of chapters in the chapter settings.

Good to know
You can also change the settings directly when you create chapters and lectures.  

How to change the chapter settings:

1. Open the course in which you want to make changes.
2. Click on the chapter in which you want to make changes.
   A page will open where you can modify the settings.
3. Edit the settings:
• Chapter thumbnail (optional): Image for the preview on the course homepage in the Chapter thumbnails and Course content
  components.Members can see this image.
• Upload image: Opens a window in which you can select or upload an image.
  The image appears on the course homepage in the chapter thumbnails and course content components.
• Chapter title: Name of the chapter.
• Chapter route: Path for the chapter.
  By changing the path, you make the content easier to find.
4. Click on Save.