Hey all. if you have a gallery block in 7.1, I have managed to make the caption overlay the image quite successfully, whilst having hover effects applied aswell. The easiest way to do this is add HTML text to the caption itself. This allows you to have much more control over the text and font without the need to apply 100 lines of CSS.
Images attached are of my new website. You can see the text overlay and on the second image, you can see the hover effect. This was all done using simple CSS. If you want text to appear and rise perhaps on hover, that once again is extremely simple