No, this is not possible. You can only use the font icons which are bundled with the theme at the moment. Kriesi is working on some improvements so maybe it will be possible to use custom icons/images in the future.
you can try to implement this like described here:
I have used it with CORONA, but have not yet tried it with ENFOLD – but it should work.
You just need to place
<link href="//netdna.bootstrapcdn.com/twitter-bootstrap/2.3.2/css/bootstrap-combined.no-icons.min.css" rel="stylesheet">
<link href="//netdna.bootstrapcdn.com/font-awesome/3.2.1/css/font-awesome.css" rel="stylesheet">
in the header and in your page something like that:
<i class="icon-camera-retro" style="color:#A882BD"></i> icon-camera-retro
The options are all described at the link, mentioned above.