The Mac OS theme will be returning, but I'm going to re-write it for phpBB 3 and launch it with that. The version we had running before isn't compatible with this version of phpBB 2 (at least, not without a significant amount of work) due to the fact that we were running an older version of phpBB 2 than this one before.
The postcount/avatars thing was something we decided to try out. Hopefully not having the postcounts will avoid any postcount++... and since the old ranks were intrinsically tied to the postcounts, it doesn't make much sense to have those, so we decided to offer everyone avatars.