Call WP Modal Login with image instead of text – PHP

http://wordpress.org/plugins/wp-modal-login/

http://wp-modal-login.colegeissinger.com/

add_modal_login_button( $login_text = 'Login', $logout_text = 'Logout', $logout_url = '', $show_admin = true)

I am using the above code (with different set values) that I received from the 2nd link from the top… it creates a hyperlink to call the WP Modal Login window via PHP. Basically, it is used for calling it on a custom page, which I am currently doing.

I have found that the text hyperlink that the code snippet creates to open the modal window for logging in sorta blends in with the rest of the site, so I want to use a hyperlinked image that I have created instead. Unfortunately, my programming knowledge is highly limited and I have no clue what to do here

Would someone be able to help me out with this? Please respond ASAP. Thanks in advance!