If you would like to select a specific page or panel to feature as the thumbnail image for your manga, you can do so using the desktop version of pixiv.
The mobile and app versions of pixiv do not currently support this feature.
The procedure for selecting the thumbnail is explained below.
How to set the thumbnail for a new post
How to change the thumbnail for a previously posted work
＜How to set the thumbnail for a new post＞
1. Select "Post your work" from the top menu on the pixiv main page
2. Select "Manga" and click "Select files" to upload your work
3. Click the "Adjust" button in the thumbnail field
4. Select your preferred page or panel and click "Apply" to set the thumbnail
[I want to select a specific page]
By clicking the right and left page scroll buttons (＜ and ＞), you can select the page you'd like to use as a thumbnail.
[I want to select a specific panel]
You can drag images to create a thumbnail of a specific panel.
You can click and drag the four corners of the image to make the selected area larger or smaller.
＜How to change the thumbnail for a previously posted work＞
pixiv Premium members can repost a work via that work's details page.
1. Go to the dashboard and click on the pen icon for the work for which you'd like to change the thumbnail
2. Click "Resubmit artwork"
3. Click the "Adjust" button in the thumbnail field
4. From the thumbnail edit page, select your preferred page or frame and click "Apply" to set the thumbnail