To opt into the beta, and try themes, join the Google+ community and then use the opt-in links in the community sidebar. Then Google Play will serve you the alpha/beta APKs.
Copyright 2013 Andrew Shu Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.