I had written a hack for my client, and would love to share.
Auto detecting Joomfish languages with your K2 Component, making your attachment number of field to match with JoomFish Component site languages.
Please follow the below steps to achieve this.

www.designersandbox.com/joomla/adding-multiple-attachment-for-joomla-k2-component-according-to-the-number-of-joomfishs-language/