To the OP...
A "TGP2" was a dumb idea that failed back 15 years ago. It was essentially a TGP with no full nudity or sex in any of the picture galleries.
I'm not really sure what you are asking about.
I THINK you might be asking about TGP's that have thumbnails on the page for each gallery?
TGP's were originally text links to galleries.
A few years back several TGP's started using thumbs on the main page for each gallery.
We didn't do it at the time because we were worried about 2257 laws and being a "secondary producer" etc., etc
Once that lawyer-generated scare tactic bullshit faded away...a lot of TPG's went with thumbnails for each gallery.
I recently did the same. But finding the software to do so is a real bitch. Since TGP's are dead in comparison to what they once were...the companies that made that software haven't made it in years.
I'm now using Wordpress with the "Adult Gallery Press" plugin
http://www.adultgallerypress.com/
It has some bugs here and there...but I figured out how to make it work correctly.
Here are my TPG's using it:
http://shavedgoat.com
http://grampland.com
I haven't done any real design work on either site yet because I'm busy inputting galleries into the queue to run everyday.
Anyway, if that's what you're asking about...that's the solution that I found.