I have set up a child theme of the twentyten theme. In the themes section that under the appearance, I can only see the child theme’s title, author name, and a grey box above it. How can I add an icon/image to be displayed in the grey box?
Leave a file with the name screenshot.png inside the root of your child theme folder and it works.
The recommended image size is 600×450. The screenshot will only be shown as 300×225, but the double-sized image allows for high-resolution viewing on HiDPI displays.
- see on Codex