theres 3 races for each side:
chaos (daemons that use their chaotic powers to transform themselves, etc.)
Dark Elves (don't know much about them, sorry)
Greenskins (Orks and Goblins, very crafty and very bloodthirsty xD)
Humans (same ole same ole)
High Elves (don't know much about them either)
Dwarves (masters at engineering, runes, etc.)
Also, quests are going to be completely different....just go watch the latest podcast, located here:
http://www.warhammeronline.com/english/media/podcast/
click Podcast #7.
Also, you can level up by pure PvPing....just as fast maybe even faster than PvE grinding. Also, PvPing at low levels helps out the high levels with their PvPs, just watch Podcast #3 for info about that...
Basically, just watch all the podcasts...they are all badass...and that Paul guy that does them needs a raise or something xD
And yes, there will be Marshes (greenskins starting areas) snowy areas (dwarven areas) but I highly doubt they will make 'pastures' as you speak of. The entire planet is constantly at war with one another....and every zone you go into will have battlefields, PvP, etc. etc.
Anyways, just watch the podcasts....#3, #5, and #7 for detailed info about the game...it just looks badass =D
Also...the Warhammer universe was out over 10 years before the Warcraft universe....so...yea ^^