Here is a short guide on how to set your Minecraft server's icon:

1. First, you will need to create an image and then modify it so its dimensions are 64x64 pixels and its file extension is .png (this tool will be useful to do this task).
    

2. Then you will need to rename your icon to "server-icon.png".

3. Finally, go to the "Files" section of the LRT Game Server Panel and drag-and-drop the "server-icon.png" there.

4. Restart your server and your icon should now be visible on your player's server list!