When you set up a Group, a landing page where you show all the promotions is created. You can customize this landing page with some different images that we describe below with their characteristics:
1. Header image. Sizes: 810px width x 360px height.
2. Promotion image in Group's landing page. 300px widht x 245px height.
3. Background. The background image from the master promotion is used.
To submmit these images and customize the landing page with code, follow the settings instructions of this link.