Hey!

I see some invalid markup therefore the slash . See screenshot: http://prntscr.com/4uutjl . Did you try editing any theme code ?. 

As regards the icon. You can put in an icon via the Salient Theme Options and provide me a link of the 500px icon so i can provide you relevant css to replace that particular icon that you choose. 

Thanks

You need to add a slash at the end cuz what you have right now is invalid markup . So img tag would look like this :

<img src='' />

For the Icon , Add this into the Custom CSS box located in your Salient Options panel :

#footer-outer i.icon-flickr {
    background: url(http://preetkatta.com/wp-content/uploads/2014/10/500px-4-256-e1412965878637.png);
    width: 33px !important;
    background-size: 100%;
}
#footer-outer i.icon-flickr:before {
    opacity: 0 !important;
}

Thanks