add a second "subtitle" line to image description and custom fonts

i am in the process of moving from 7.0 to 7.1 and am redesigning my new site. I have added some custom CSS to mosaic gallery page to allow a hover effect which shows the image description on hover. I am a painter and what I would like ideally is for the description to have to lines, like the title of the work in one font and below it in a different size and possibly different font, the info of the painting (medium year size). Is there a way to add a second sort-of "subtitle" section into the image description that can make this a reality? I don't knw how to share the under construction site bc it isn't published yet. Thanks!

Step 1. In Description, enter this format

Quote

Your title <span>sub title</span>

Step 2. Share link to gallery page, we will give the code to break sub title to new line