James Revillini

A major drawback to using Elementor is that the background images used for sections and columns are all loaded when the page loads. Using a plugin like WP Rocket or BJ Lazy Load will not solve this issue. This plugin fixes that.
The plugin is dead simple. No extra database tables or queries, no admin screens with difficult options to understand, and no dependencies other than that the page is designed with Elementor. It injects a little JavaScript and CSS on the front-end. The CSS hides all backgrounds on all non-animated sections and columns. The JavaScript detects the visitor’s scrolling and starts loading the background images as they get close to those sections/columns using the WayPoints JS library (which is packaged with Elementor).
New
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<li>support has been added for the following Elementor Pro elements: Flip Box and Slider – thanks for the idea @dollhauss</li>
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Lazy Load Elementor Background Images

Lazy load background images of Elementor sections, columns, and some elements. Compatible with Elementor Pro.

yasir129

Lazy Optimization plugin is the first ever WordPress plugin to lazy load background images that are in external CSS files. 
Lazy Optimization plugin works on top of Autoptimize plugin and is used to lazy load background images that are present in Autoptimize external CSS files. 
Lazy Optimization plugin replace all the background images that are in Autoptimze external CSS files with a dummy image and when the element with the background image comes in viewport it’s original background images gets loaded.
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Dependices <a href="https://wordpress.org/plugins/autoptimize/" rel="ugc">Autoptimize</a>.
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<iframe loading="lazy" class="youtube-player" width="750" height="422" src="https://www.youtube.com/embed/5Enr7OHNtIQ?version=3&rel=1&showsearch=0&showinfo=1&iv_load_policy=1&fs=1&hl=en-US&autohide=2&wmode=transparent" allowfullscreen="true" style="border:0;" sandbox="allow-scripts allow-same-origin allow-popups allow-presentation allow-popups-to-escape-sandbox"></iframe>

Lazy Optimization

Lazy Optimization speeds up your website by lazy loading background images that are in the external CSS files.

Lazy Load Elementor Background Images vs Lazy Optimization