The following method was tested with FreeBSD 10.0 image bundled into Icehouse version of OpenStack running on Ubuntu 14.04
Create an image needed for Hard-drive emulation
qemu-img create -f qcow2 freebsd.img 5G
Start the Virtual Machine to boot from the CD.
kvm -m 512 -cdrom FreeBSD-10.0-RELEASE-amd64-disc1.iso -drive file=freebsd.img,if=virtio -boot d -net nic -net user -nographic -vnc :1
Connect to the Virtual Machine through VNC (use display number :1) where 10.10.10.1 is the IP address of the host machine.
vncviewer 10.10.10.1 :1
After installation is over, during the post-installation configuration enable SSH server, IPV4 and DHCP. Shutdown the Virtual Machine and use the following command to boot from the hard drive.
kvm -m 1024 -drive file=freebsd.img -boot c -net nic -net user -nographic -vnc :1
Add the following line to /etc/rc.conf
Edit the following lines as below in /etc/ssh/sshd_config, for SSH access as root and to enable password authentication.
PermitRootLogin yes PasswordAuthentication yes
Do the other necessary changes needed for the image and shutdown the Virtual Machine.
Shutdown the Virtual Machine and upload the image to OpenStack using Horizon or Glance commands.