After creating your video, it will automatically save as a draft under the Create tab. If you'd like to change your video thumbnail, you would need to save your video and change the thumbnail the same way you would any other Vimeo video in the Library:
1. After finishing your video, click on Save & share.
2. In the Vimeo Library, select your video, then click Settings to the right of the player.
3. Under the General tab, scroll down and click on Edit thumbnail.
4. Choose from the three options available and then click on Save.
Note: You can also edit the thumbnail in the video edit page by clicking the Player button to the right of the player, and then open the Thumbnail menu that appears above the player.