How to show animated gif on mouse over/hover in the index page? *Avenue Template*

Site URL: http://www.millerbest.com/

Hey guys,

I currently have a website made with Avenue template. The home page is an index page, which features a variety of different images that click through to other pages. I currently have the 'show caption on hover' setting, but I'd love to get an animated gif playing/looping when hovering/mouse over. Is this possible? I've searched through the forum and found a few leads, but I'm not sure I understand where to embed the custom CSS and where to upload the gif etc. 

Thanks!

Ever figure this out?