Packer
Proxmox Builder
The Proxmox Packer builder is able to create Proxmox virtual machines and store them as new Proxmox Virutal Machine images.
Packer is able to target both ISO and existing Cloud-Init images:
proxmox-clone - The proxmox image Packer builder is able to create new images for use with Proxmox VE. The builder takes a cloud-init enabled virtual machine template name, runs any provisioning necessary on the image after launching it, then creates a virtual machine template.
proxmox-iso - The proxmox Packer builder is able to create new images for use with Proxmox VE. The builder takes an ISO source, runs any provisioning necessary on the image after launching it, then creates a virtual machine template.