To resize a qcow2 image, download the latest release of qemu (> qemu 0.13.0) compile it, and resize the image. If you run a Windows OS inside the .qcow2, you need to adjust the additional storage in the Disk Management.
If you like to expand a Boot partition, download the GParted Live CD .iso and boot your vm-103-disk-1.qcow2 with the GParted Live CD.
Expand the Partition and you’re done.

vmonster:/home/images/103# qemu-img resize vm-103-disk-1.qcow2 +5G