Justin I do front and backend. I prefer to use Node but I can work with PHP and Ruby. I also am a decent sysadmin, and know Cassandra and mySQL.
I'm most interested in seeing how you plan to store all these images longterm and provide constant uptime on all of them. I presume you use a CDN (Cloudflare from my basic lookover) for delivery but are you storing them on a cloud provider or using some sort of local RAID setup? With these cheap $150 8TB disks available now I have been pondering setting up some sort of local image host that is served over a CDN.