OpenStack images for Ubuntu are available from cloudbase.it, including images for:
Follow the local setup instructions before starting.
Download image from the above URL, then run:
openstack image create --file trusty-server-cloudimg-amd64-disk1.img --disk-format raw "Ubuntu 14.04"
openstack image create --file xenial-server-cloudimg-amd64-disk1.img --disk-format raw "Ubuntu 16.04"
openstack image create --file zesty-server-cloudimg-amd64.img --disk-format raw "Ubuntu 17.04"