Can you add support for capes from that website?
This not works with the CustomSkinAPI because needs the player's uuid.

The api call is pretty simple:

http://minecraftcapes.co.uk/getCape/{UUID}

Could you provide a UUID for example?

For example the uuid from a guy named user is: 'ef5db304-c368-4108-9a35-2fd0a072b73d'
The API call need to be without the dashes, eg:

http://minecraftcapes.co.uk/getCape/ef5db304c36841089a352fd0a072b73d

As this page only work with premium users (it's like optifine but for custom capes), for get the UUID you need to verify with the Mojang API.

Using the Mojang API for get the UUID will be:

https://api.mojang.com/users/profiles/minecraft/{USERNAME}
https://api.mojang.com/users/profiles/minecraft/user

How to use minecraftcapes.co.uk

• Turn on forceLoadAllTextures

"forceLoadAllTextures": true

• Add it in loadlist

{
  "name": "minecraftcapes",
  "type": "legacy",
  "cape": "http://minecraftcapes.co.uk/getCape/{UUID}"
}

Please make a review.

Tested!
Works properly in secure and insecure servers!

Notice that minecraftcapes.co.uk has changed thier API:

{
    "name": "MinecraftCapes",
    "type": "Legacy",
    "checkPNG": true,
    "cape": "https://minecraftcapes.net/profile/{UUID}/cape"
}