Munkelzahn said:
I knew it!
Adding the direct link to the sources is good for something.

Yep.. Those would've been extremely useful now.
Old direct links still work if you change the subdomain, but same cannot be said about other Tumblr sources: tons of deleted or moved accounts, etc. The images are probably still out there somewhere, but in many cases we have no way to find them.

Reverse image searches don't work, and Tumblr is excluded from Internet Archive, etc. Nothing that can be done now, as far as I can see.