Localcape

localcape is a simple mod that allows you to define custom capes that will be displayed on your client only.

Capes are added inside the config directory, under the localcape folder, where you must put the cape texture with the username of the player you would like to show that cape on.

Where do I find capes?

The Minecraft Wiki has a page on all the official minecraft capes. From there you can click on one you like and download the texture.
If you do not want any of these, you can create your own.
Tools like Autocape exist, however I have not personally used them.

I recommend searching up a cape template and making your own inside a program like Paint.NET.

Troubleshooting

My cape isn't showing up! What do I do?

If your cape isn't showing up, there are a few steps you can take.

1. Make sure that your cape follows the proper 64x32 minecraft format, not some other one.
2. Make sure that your cape is named the right filename, e.g. MyUsername.png and is inside the right directory, localcape.
3. Finally, if none of those work, check the logs. You might see an error message with more detail on why it failed.