Changing the Login Box Skin
Search for a Skin
Head to NameMC (opens in a new tab) and enter a player name or simple term that you want the skin to feature.
Enter the "Skins" Section
Click the search button, and then click the link under the "skins" section.
Find a Good Skin
Click on a skin that you like from the list that pops up (if you can't find a good one, try a different search term)
Obtain Link
WITHOUT ROTATING THE SKIN, click the photo icon. Copy the URL of the page that opens AFTER clicking the photo icon. This is the example URL (should look like this): https://s.namemc.com/3d/skin/body.png?id=5f4d90f8c5debd19&model=slim&theta=30&phi=21&time=90&width=600&height=800 (opens in a new tab)
Open Template Page
Under the template (opens in a new tab) section the Tebex panel, click "edit".
Change Setting
Under options -> general settings -> "Login Box - Minecraft Skin URL", paste the link that you copied from NameMC, and click the save and publish button.