Bharat Bhola

This plugin allow to upload multiple images for posts, pages or custom post. easy to enable/disable image upload option in post, page and custom post type. Also you can arrange images order using drag and drop.
<h3>get_miu_images()</h3>
This function can be called from any template file to get attached images for the page/post being viewed. 
It returns an array of the attached image URL or attached ID.
It take only one argument and it is default:
<ol>
<li>post_id (integer) to get images linked to a specific post or default take current post images</li>
</ol>

Multiple Image Upload

This plugin allow to upload multiple images for posts, pages or custom post. easy to enable/disable image upload option in post, page and custom post  …

Yannick Lefebvre

The purpose of this plugin is to allow users to create one or more modal dialog(s) / pop-up window(s) that will appear when a user visits their site. The number of times that these can load is configurable. They can load content from external sites or custom HTML code into the dialog. This plugin can be used to invite people to register to a newsletter, respond to a survey, or simply welcome come to a site upon their first visit.
You can try it out in a temporary copy of WordPress <a href="https://demo.tastewp.com/modal-dialog" rel="nofollow ugc">here</a>.

Modal Dialog

The others either didn't work or caused massive JavaScript problems, breaking other plugins.

This plugin worked the best.

Worked better than the others

The purpose of this plugin is to allow users to create one or more modal dialog(s) / pop-up window(s) that will appear when a user visits their site.

Multiple Image Upload vs Modal Dialog