The client image library panel shows the images that reside in the repository on the client.
This panel exists mainly for debugging purposes. When the client connects to the server, all applicable components in the server's repository are sent to the client, so the images in this repository should match what you see on the server.
The checkbox at the top of the panel toggles whether or not core images are displayed in the table.
The client image library panel is a sub panel of the client component library panel.