ImagesToLinks.user.js

// ==UserScript==
// @name        Images to Links
// @namespace   http://www.github.com/jaaaaaaaaaam
// @description Changes images to links of themselves if they do not have a parent <a> tag
// @include     http://*
// @include     https://*
// @require     https://code.jquery.com/jquery-1.11.3.min.js
// @grant       none
// ==/UserScript==

$('img').each(function () {
    if(!$(this).parent().is('a')){
        $(this).wrap(function () {
            return "<a href='"+$(this).attr('src')+"' target='_blank'></a>";
        })
    }
})