Actually it’s possible to do it by few different ways. When you configure gallery images you can fill text fields which could be customizes or used later in layout of the hover elements of the gallery photos.
You do not required to customize CSS. Just open gallery settings and scroll to the hover settings. There you can switch on text fields which you wish to show on hover.
Another, alternative mode it’s hover template which give you more freedom.
Gallery hover template have build-in tags which could be used in template field in combination with the text and HTML tags. In gallery hover template customization you don’t have any limits.
