[Plugin: NextGEN Gallery] Description over thumbnail

Hello,

I use a ngg gallery (v 2.0.66.33) on my Origami theme to show my illustrations on my website.
I would like to display the title and/or description over the thumbnails when hover on it.
I can change thumbnail’s behaviour (brightness, drop shadow…) on rollover but i didn’t fund solution to display the title/description on it.
I want to do that with css style and maybe some html on the page, but i want to avoid changing ngg’s php code.

Here’s the concerned website’s page: https://samygeminel.com/images/

I’m a fresh new user, my knowledges in coding are so baaaaad!!

Someone has an idea??

Thanks a lot!