Hi Randall,
First of all Edit the column -> Check the Advanced checkbox -> Here you can find background upper layer and background lower layer option. Add the image at any layer.
To add image or colour overlay on column hover it would require custom development I would suggest you consult a developer who can assist you with your concern or you can avail of our newly launched service called One, where the customization questions are answered.
If you have an idea about CSS coding you take the reference from these article.
Please follow this link to add an overlay to the background image.
You can adjust the overlay darkness using opacity
Please note that we do not provide custom development support. it is out of the support scope.
Thanks for understanding