M, the Toshinden cover art was found on the main page Battle Arena Toshinden Wiki.
Here.
I was surprised to even find that. Toshinden and Darkstalkers being long-box titles meant finding art appropriate & period that wouldn't stretch-and-squash for a standard 4:3 insert jewel case.
I'd mulled over trying to replicate the goofy screenshot used on the PSX, Saturn, or PC case before finding that emblem.
Seems to come from the European PAL PSX version.
A lot of art that used to be hosted is just gone. Since KOFOnline closed, kawaiidream.net has also restricted access to a lot of their art archives.
Fighter's Generation was also of some help.
SNKPlaymore still has their history of KOF site up. But, the art available for download isn't the same size as the promo material for when the stuff first came out.
I know full well that PSX Darkstalkers 1 isn't great fare. This was never about the quality of the games.
Had a Saturn some years ago and decided to get rid of stuff. When it came to culling out systems for space, the PlayStation stuff got kept while the Saturn got sold off.
I just wanted inserts I could put into jewel cases to look half-decent.
This was something I wanted to do then with Saturn titles to replace the fragile boxes with DVD cases.
That's Fighter's Edge logo was a pain to put together. I abandoned the idea and decided to model most of these after the more-visually-interesting Japanese cases than what we got in the US.
KOF 95 took some styling cues from scans of the European NGCD version, I think. It's been a while since I put it together. Though, the text is from the UK PlayStation release? The barcode should the the US SKU.
Darkstalkers 3 I thought looked better with the pure arcade poster - the PSX release makes the background of that image purple to hide B.B. Hood's shadow. Fun fact - the game has a folder full of BMP files in it for the characters and some extra arts. Characters also had white backgrounds. Meaning I couldn't use them to stack and recreate the US jewel back at the time. I probably could now that I've spent more time with the art program. But, I'm happy with what I've got.
Puzzle Fighter, I just couldn't find the Ryu art. I could find what I used and figured pink was a good enough color for the background. I took screenshots of the gems and just flipped them around in a pattern that couldn't create a supergem for the background. There's a layer of translucent yellow between them and the text to make the gems softer and the text readable.
DOA2 Hardcore's art is right of the DOA wiki.
Most of the art there is labeled as being from DOA2 somewhere on the image. So, serendipity and taste determined what got chosen there.