Doubt that anyone will see this but...

http://www.amazon.co.jp/ミリ姫大戦イラスト集1-重装甲編-株式会社ヘッドロック/dp/480220177X


the artbook is up for sale, for about 30 bucks for me atleast. Amazon JP does ship internationally but you'll need to create an Amazon JP account first which is simple. It seems like it will be split into two volumes, with this being the first.