The "en" denotes the language and is added to all files except the 3D (pvz).
This is done to identify which file is which language when publishing to multiple languages.
The 3D pvz file doesn't need to language as all languages are in the one file and you can switch between languages in Creo View.
The "I" & "s" denotes where the publish setting that created the file came from, I for a local preference and s for a shared preference.
I'm afraid they are always added to the file names.
Hope this helps.