One of today's changes for the upcoming WSN 9.2.37 is a set of new template variables that provide easier ways to reference files attached to an image in a specific order (the sort order set on upload/edit). There's now {LINKTHUMBIMAGEX[number]}, {LINKTHUMBURLX[number]}, and the associated boolean {LINKHASFILEX[number]}. You can pair these with the preexisting {LINKCAPTION[number]} and {LINKHASCAPTION[number]}. If you want to show the third image on a listing, and include the caption only if it's present, here's all you have to do now:
<IF {LINKHASFILEX[3]}>
{LINKTHUMBIMAGEX[3]}
<IF {LINKHASCAPTION[3]}><br>Caption: {LINKCAPTION[3]}</IF>
</IF>

To change the thumbnail size away from the default, add width and height parameters... 500 width by 400 height for example:
<IF {LINKHASFILEX[3]}>
{LINKTHUMBIMAGEX[3 <,> 500 <,> 400]}
<IF {LINKHASCAPTION[3]}><br>Caption: {LINKCAPTION[3]}</IF>
</IF>

This can be very useful if you want to position large thumbnails in different places on the details page, with information around them.