Image Video Icon – change?

Hi,

i tried the demo of the pro-version and wanted to change the Image view icon to a heart (e.g.). I used this site >> fortawesome.github.io/Font-Awesome/icons/ and used the name “fa-heart”. The heart-icon showed up in my gallery settings but it doesnt show up in the gallery on my website.

What can i do to change the image view icon?

https://wordpress.org/plugins/responsive-photo-gallery/