change mouse over portfolio grid

In the portfolio grid you get on the mouse over tree dots (...) where you can click to go to the item. Is it possible to show a single line of text in stead of just the tree dots?

Always same text or different text according to article/k2 item content?

depending on the article

I would like to add a single line description per photo
preferably with something else then the intro / text of the item.

I's not that easy as there is no such implementation done. You would need to edit category page layout and add this feature there. Sadly I can only point you into right direction, we don't do this kind of customisations as a part of our technical support.