Just checked the official game site and Dengeki. There are some pictures for the 4 already known heroines based on previous news and scan (Kirino, Ruri as Shironeko, Kanako, and Sena), some CGs, and Kanako's Live 2D sprites. Here if you haven't seen them...
http://oreimo-game.channel.or.jp/
http://news.dengeki.com/elem/000/000/412/412105/
http://news.dengeki.com/elem/000/000/414/414175/
CMIIW, but from what I understand from the Dengeki article, on this sequel Kanako is the main heroine?
Are there only those 4 main routes/heroines now? I hope they will announce the release date and more heroines/characters soon...