In this tutorial we will see how to create your own cusom templates to customize the apparence of the gallery and modify a bit some details. you will need fort this a bit knowledge of PHP, HTML and CSS.
1 - Create a copy of the custom template.
First of all we wil create a custom templates that will be attached to your website, not the addon. Like this you will upgrade the addon how many times you want without loosing your edit. TO do that :
The code seems to be complicated but it's relativly simple and like any other gallery addon. Here some details on variable available
$options->galleryColumns : The number of columns choosed in the advanced options
$thumbnailUrl : The url of the Thumbnail
$fullUrl : The url of the full width image
$ratio : if the image are vertical or horizontal or square
Here a very simple starting point to your own gallery template to play with. It contains only basic variables needed to start a good gallery : https://github.com/myconcretelab/easy-gallery_templates/blob/master/basic.php
Good Luck !