Please in future post your solutions for others to see. Someone may have the same question.
Anyways, there are multiple ways to do it, for example:
&view_gallery=`docidhere` &limit=`1`
&gal_query_ids=`docidhere` &limit=`1`
Use childgallery display mode.
Etc..
Then you probably want to make custom &galleryPictureTpl for that call too that redirects to the gallery document from the thumbnail. Eg. make the link from thumbnail be <a href="[~[+maxigallery.picture.gal_id+]~]">.....</a>
"He can have a lollipop any time he wants to. That's what it means to be a programmer."