Image uploads working.
The file system changes may take a little while to be reflected on all the servers, so if it doesn't work for you, refresh and try again.
In other words, does it look like the screen shot in here; https://support.cloudflare.com/hc/en-us/articles/200171846-Why-am-I-getting-a-cloudflare-nginx-502-or-504-gateway-error