What Wendy pointed out is the method to include an image inside the biography. Unfortunately, Wikitree doesn't show on the image pages how to link as a source, as you're requesting, but it is straightforward if you know the syntax.
1. Get the name of the file from the image page. From one of yours, Allaire-7.png.
2. The syntax is [[:image:<ImageName>|<LinkDescription>]]. For your file, something like [[:image:Allaire-7.png|Link]] or [[:image:Allaire-7.png|François Alaire Tanquay Collection Vol 1 page 3]]. Whatever is entered after the pipe symbol, |, is what will be displayed on the page as a hyperlink.
3. You can use it in a source or ref entry, just as you would for any other source with a link:
* Doe, John. [[:image:Allaire-7.png|This Is My Book Name]], p. 23
* The Kalamazoo Times, [[:image:Allaire-7.png|How To Link To An Image Source]], 11 Nov 1793,
<ref>François Alaire Tanquay Collection, Vol 1, [[:image:Allaire-7.png|page 3]]</ref>