OptiFine on Twitter: "Website is back up, and broken capes should be fixed. There is also a new "Banners" tab where you can view the most popular OptiFine banner cape designs currently.
I came up with some pretty clean black and white Optifine cape designs : r/ Minecraft
Popular OptiFine capes - MCSkinHistory.com
The Strange Mysteries of the Unique OptiFine Capes - YouTube