What I did to get the Galaxy S2 skin to work with the Android Virtual Device (AVD) was:

1. download the skin from the Samsung Developer website, it’s under the Add-on SDKs,
2. extract to a Galaxy_S2 directory,
3. put the entire directory in the [Android-SDK directory]/platforms/android-10/skins directory,
4. edit the manifest.ini and change api=9 to api=10,
5. restart AVD Manager,
6. under skin in the device configuration you should see Galaxy_S2 in the dropdown.