The two Killzone 2 maps that make up the Killzone 3 Retro Map Pack have been named. They are Salamun Market and Blood Gracht.
Salamun Market is massive, according to the European PlayStation blog - a warground for up to 24 people. The Helghast apparently ambushed an ISA convoy on the main road and vicious fighting quickly dominated the market district.
Blood Gracht is smaller and supports up to 16 players. Thematically, there's loads of Helghan plant life creeping between the cityscape, making for much sneaky Guerrilla warfare.
The Retro Map Pack is given free to anyone pre-ordering Killzone 3. Alternatively, you can buy the Retro Map Pack from the PlayStation Store.
A Killzone 3 demo was released this morning. I'm playing it right now as I type, backwards, with no hands.