What package name should I use for a Cyanogenmod theme? I want to make cm11 theme.

But one problem: package name.

How does it work? Dialer package has com.android.dialer, so my package could have name eu.mikroskeem.colormelt?
I don't know about CM themes in particular, but Android app package names are based on Java packages, which means they have to start with a web domain you own, in big-endian order. That is, if and only if you own the domain mikroskeem.eu, you can use any package name starting eu.mikroskeem.

There's no way to enforce this convention, but following it makes sure that package names are unique.