I installed windows server 2012 in a virtual machine on Debian Wheezy by using kvm-qemu and by using virt-manager to manage and access it.
If you already did it, you noted the poor performance for the video and the low resolution. You cannot display a youtube video for example.
I read that SPICE can improve all this stuff but I didn't find any information to install and configure it correctly, side guest.

Acording to the spice-space.org site the spice-guest-tool-0.74 is available for windows 2012 but this tool doesn't recognize windows 2012 !

Another approch is to install manually the driver windows QXL driver by selecting this for windows 2012,

and the agent windows SPICE agent, last version.

Unfortunately there is no documentation !
The driver package has the cat/inf/sys/dll files. The command pnputil -i -a qxl.inf refuses to install the driver !
The agent package has no exe file !

WHO was able to use SPICE on Debian-KVM-QEMU with a windows 2012 guest ?
WHO could explain, from A to Z, how to proceed ?

Zhank you by advance

Sorry I don't use this configuration but have you tried the virtio driver iso? http://alt.fedoraproject.org/pub/alt...latest/images/

It seems that there are some drivers here:

http://people.redhat.com/~vrozenfe/qxlwddm/

I tried it on a Win 8.1 32 bit machine, the driver loaded runtime but after reboot froze the console (rdp was ok). I installed it from the Device Manager GUI.

Edit:
for clipboard sync + dynamic graphical resolution change you have to use vdagent (which works on all versions of Windows i tried on).