In the lightbox, hit the Change button from Custom Tab Image.
Hover cursor over the logo and hit Edit.
In the lightbox click on Choose File to upload the image you want. Note: The image has to be of exactly 111 pixels in width and 74 pixels in height, respectively. If the image doesn’t have these measures, or is larger than 1 MB, your upload will fail.
The new tab image will saved automatically after you have uploaded your image. You can view your tab back in the Admin Panel. You can also change the tab name with any text you want.