If you’re interested, it is actually fully possible to do this over the web, but as Jaymes says, would require some customization. I believe, have not tested this means, that all you’d have to do is change all the references of IPs to hostnames. In /tftpboot/default.ipxe there’s one line that would need to be changed on the server. You either change it to the externally accessible IP or FQDN. On the fog GUI side you’d need to change the IP of storage management page on your node to the externally accessible IP or FQDN. Finally you’d make the change in FOG Configuration->FOG Settings->tftp server and web server to be that of the externally accessible IP or FQDN. This should enable uploading across the internet as well as downloading images, or any task for that matter.

Again, I haven’t tested it fully, but it already exists with minimal changes. It looks like a long block of text but in steps its really only 4 items to change.