https://jimboy3100.github.io/skinrotator.html

-Use custom skins by agario AUTO-updateable skin library
-Design animated skins from the library, choose how whow quick/slow they can must be changed
-Use generated code as Script on Console
-Use generated code as your a new Userscript

*This webpages generates code, compatible with all known extensions!
**Known issues:
-Name should be used
-If using Legend Mod, do not use any backgroud because the bold grid will appear. Use Default Template, enable vanilla skins and your name
-For generated Userscripts compatibility with other mods you may need (for developers):
...
 // @grant none
 // ==/UserScript==
...
setInterval(function() { // put this after the above code
//Put here the rest code
}, 100); //as 100, it is 0.1 sec, find the exact timing for compatibility

Similar projects (libraries) for all extensions:
Custom skins: https://jimboy3100.github.io/skins/
Skin Checker: https://jimboy3100.github.io/skins/skinchecker.html