[Plugin: WP Favorite Posts] Just Image instead of add to favorites text?

Hello,

I want to use a hollow star as “Add to favorites” link and a filled in star as “Added to Favorites” is this possible in the current version?

I saw it mentioned here but I’m still not sure how to do this:
http://wordpress.org/support/topic/plugin-wp-favorite-posts-adding-an-image?replies=3

http://wordpress.org/extend/plugins/wp-favorite-posts/