Hi !
I finally found the solution with an other post on the forum ...
I put this code in the html layout :
<li id='psimg_[image_id]' class='psgal_[gallery_id]' style='width: 33%; height: 200px;'>
<div class='bwbps_image_div' style='width: 129px;'>
[thumbnail]
[caption] da : [user_name]
</div>
And this one in the wrapper :
<div class='bwbps_gallery_div'>
<table>
<tbody>
<tr>
<td>
<ul class='bwbps_gallery'>
[gallery]
</td>
</tr>
</table>
</div>
So, finally, like that, the thumbnails are opening in a lightbox, and when we click on the caption and author name, it is opening the attachment page.
Perhaps it will help someone else !
Thanks again for all !
Laurence