using grid for pure custom html

i'm using the grid module for pure html

and i'd like to add an image with some text over the top and link that image. for example purposes, i'm using this setup:

http://demo.gavick.com/joomla25/msocial ... uration-ii

the box under the video that says you can add video too ... how would i add an image in there, that filled the whole box (in desktop view and mobile/tablet view) with text over the top that I could link??

i'm asking the question rather than describing my problem as i think it will be easier

thanks

i'm adding the custom background image and using the suffix gkPhoto in the options

and in the custom html i'm adding:

<a href="#"><h3 class="gkCentered">MY TEXT HERE</h3></a>

but i'm not seeing any text ...

sorry for repeated posts

i guess what i'd like is to make the whole module linkable with my text in the module .. much like the social icon modules are linkable. is that possible?