Regarding the artillery sound: In my gaming experience I've come across a lot of games with artillery in it. But the one game that nailed it for me the best was in Total Annhilation. It just had that deep and rich firing sound after which you knew you just messed something big up for your opponent ...
The map preview is great in general. But one thing I've always missed when I was starting a new session: The player spawn point. I think this should show up in the preview as well.