Since Minecraft 1.7.2 you have been able to add a server icon to your server that players can see from the server list screen.
Make your server icon. You can use a program such as Gimp or PhotoShop. You will have to make a 64x64 canvas and draw a server icon.
Once you have completed the server icon go to file save as and save it as the name server-icon and make sure it is a .png file.
Drag and drop the server-icon.png into your main server directory. Now restart your server and the server icon will be there.
If following these steps does not work make sure your file size is 64x64 and it is named server-icon (icon)
To check if your file size right clicks on your image and click properties (Windows) or Get info (MAC) and fine where it says file size and it should say 64x64. If you have tried these and they have not worked please submit a ticket and someone will assist you.
Huge thanks to ThePurplePvPer for making this post.