Hi,
module code customization is not a part of support.
But I can give you 2 tips:
1) You have to edit at least one file from here: modules\mod_image_show_gk4\styles\gk_university
2) This is css style for loading - which you will find inside: modules\mod_image_show_gk4\styles\gk_university\style.css
.gkIsWrapper-gk_university .gkIsPreloader {
background: #3f4e67 url('loader.gif') no-repeat center center;
height: 100%;
left: 50%;
position: absolute;
text-indent: -9999px;
-webkit-transform: translateX(-50%);
-moz-transform: translateX(-50%);
-ms-transform: translateX(-50%);
-o-transform: translateX(-50%);
transform: translateX(-50%);
width: 100%;
z-index: 100;
}
Now your turn.