The thumbnail is defined in the bottom of the template, not in the is=`slimbox` block...
But you don’t need to keep all the conditionals in the template if you are just going to use slimbox, just put this to the chunk:
<li>
<a href="[(base_url)][+maxigallery.path_to_gal+][+maxigallery.picture.filename+]" rel="lightbox[image[+maxigallery.pageinfo.id+]set]" title="[+maxigallery.picture.title:htmlent+] - [+maxigallery.picture.descr:htmlent+]">
<img src="[+phx:input=`[(base_url)][+maxigallery.path_to_gal+]tn_[+maxigallery.picture.filename+]`:phpthumb=`ws=140&hs=105&zc=C`+]" class="thumbnail" title="[+maxigallery.picture.title:htmlent+] [+maxigallery.strings.click_to_zoom+]" alt="[+maxigallery.picture.title:htmlent+] [+maxigallery.strings.click_to_zoom+]" />
</a>
[+maxigallery.picture.title:isnot=``:then=`
<p style="width: [+maxigallery.picture_width_thumb+]px;">
[+maxigallery.picture.title:htmlent+]
</p>
`+]
</li>
"He can have a lollipop any time he wants to. That's what it means to be a programmer."
Perfect! You are an awesome help!