I have tried integrating McLighting which uses WS2812fx to provide 50+ effects. If anyone is interested, you can clone and test my fork here. Change my_led_config.h file accordingly. To control the effects using MQTT, send payload to topic cmnd/sonoff. To see results, subscribe to stat/sonoff/LED. Checkout this API for how to send payload. Don't know if it messes up other sonoff code. If you don't want to compile, flash the file firmware.bin in this repo directly to your sonoff and you are good to go. File modes.json contains the list of all the effects you can have. A simple mqtt publish to topic cmnd/sonoff with payload /<effectID> will change the animation. Hope this helps someone!