By default, a new GitHub App will have an automatically generated identicon. An identicon badge looks something like this:

After you create a GitHub App, you can customize your app's badge by uploading a logo and selecting a background color. A badge is a square logo image inside of a circular badge. You can choose a background color for the badge, which can visually distinguish your app.
Your logo should be a PNG, JPG, or GIF file under 1 MB in size. For the best quality rendering, we recommend an image size of at least 200px x 200px.
To create a custom badge:
- 任意のページの右上で、プロフィール画像をクリックし、続いてSettings(設定)をクリックしてください。 ![ユーザバーの [Settings(設定)] アイコン](https://github.github.com/docs-ghes-2.18/assets/images/settings/userbar-account-settings_post2dot12.png) 
- 左サイドバーで [Developer settings] をクリックします。  
- In the left sidebar, click GitHub Apps.  
- Select the GitHub App you want to modify.  
- In "Display information", drag-and-drop an image from a local folder or click Upload a logo to select an image from your computer.  
- 画像をクロッピングします。 When you're done, click Set new avatar.  
- In "Badge background color", type the hexadecimal color code of the background color for your badge.  