It appears to be working on Posts, and the tags show up in the Manage Gallery admin section. I can't seem to locate where NextGen stores its tags in the database though.
The NextGen plugin homepage showed a snippet of code so it could be used elsewhere, which I assume to mean on a Single.php, which is what Posts are shown on. I'd like to use that code on my theme's Tag.php (Tag archive page).
On my Tag.php I have included code from another PHP page which gets information about about that Tag from a data table that I created and maintain. (Information about basketball players.) So I'm able to carry the tagID from WordPress to that page. I'm hoping to be able to match that with the tag information from my images, which would produce related images the same way as they do on Posts.
Here is an example of what I'm talking about:
Everything from RECENT ARTICLES and above are from my custom code. I have a var_dump in there too, which reflects the WordPress tagID, in this case "72". I assumed the Tag information would match the same way as it does on Posts, but I guess it doesn't.