Display the ID/number of thumbnail

Not out of the box but with some custom development you should be able to achieve it using the easy_image_gallery_html filter.

Hi Andrew,
I just tried change or add some variable in the file template-functions.php with easy_image_galleri_count_images() , but it brings the final number of uploaded images. For ex. from 12 images I got:

<li class="thumbnail-12">...</li>
<li class="thumbnail-12">...</li>
<li class="thumbnail-12">...</li>

or when I used the ID I got the asigned number sorted from all uploaded files ever, for ex. thumbnail-1254, thumbnail-1255, etc.
but I need count from 1 to 12, like this:

<li class="thumbnail-1">...</li>
<li class="thumbnail-2">...</li>
<li class="thumbnail-3">...</li>
...

Is there any possible way to do that?

Thanks a lot for your help.