Hi,
The 14.04 release uses a different desktop environment than the 12.04 release by default. Unfortunately the new one requires 3D acceleration and the old desktop environment is no longer available in the 14.04 release.
What we've done in the 2014_R2 release of our pre-built images is to use the 14.04 nano release as a base and install the XFCE desktop environment on top of it.
- Lars