I would be now publishing my first app on Google play store. I have already compressed images used in my app. And I have some questions regarding the app size.
For those of you doing much smaller projects, consider removing all the app-compat libraries. You may be better off making multiple versions of your app for specific versions of the API. I've seen a 47Kbyte app balloon to 3Mbytes just by adding compatibility libraries.
Summary: to save space, avoid unnecessary libraries, even ones provided by Google (and included in most templates!).