'Deep Web' is a melodramatic name for sites that aren't indexed by Google. I'll use it more generally here to mean sites that deserve special attention when searching for Ulysses-related resources, especially images.
The Hathi Trust beats the pants off GoogleBooks or archive.org for breadth and usability.
The National Library has over 1000 historic pix on Flickr (searchable via a popup menu)
A Twitter account called PhotosOfDublin has posted 1000s of pix in the last year
Barger's "Internet Ulysses" (apparently once termed "a watershed in Web culture" by the Irish Times) is at archive.org (not searchable, I don't think)
Scarily detailed Irish census info for 1901 and 1911 is a little tricky to search (advanced search options include religion, and street)