>>105676681I was going to write about how someone might've archived it in the internet archive, but it seems that only his 8.1 themes pack that niivu uploaded to deviantArt after his death has survived.
https://archive.org/details/Neiio8.1pack
As far as I know - after he passed away due to medical complications, his daughter handed over all of his theming work to niivu. Neiio reuploaded them back in themepacks (like the 8.1 one), and started porting his work to be compliant with newer releases of 10, along with making his own stuff. (i think he actually ported some of them to 11 recently.)
Niivu's been doing windows 11-only visual style stuff, and removing themes that he deems "outdated". He's been kind enough to reupload them to his github, though, but that's for 10 and 11 themes only.
https://www.deviantart.com/niivu/art/neiio-s-Windows-7-Theme-Pack-Part-1-705044785
https://www.deviantart.com/niivu/art/neiio-s-Windows-7-Theme-Pack-Part-2-705048282
These defunct links show that he still had them hosted in his deviantart page. You might ask him whether he still has the packs and whether he could store them in a github repo akin to the 10 and 11 themes, but for neiio's stuff.
Or ask in the desktop ricing threads - maybe some anon still has them stored in some forgotten folder beside his cunny stash.