So I'm still fascinated that this season of Twin Peaks may inspired by some of Lynch's scrapped projects, but I am personally thinking these four projects of his are the most evident he's been pulling from:
-Ronnie Rocket
This is apparently Lynch's most thought about movie that never got made. It's one of the earliest films he ever conceived, apparently he was thinking about this movie all the way back since he was working on Eraserhead and was still thinking about it after Lost Highway. He's revised the script multiple times, with these two versions having become available online:
The version from around the time he was working on Dune:
http://www.lynchnet.com/rrscript.html
The version from around the time he was working on Wild At Heart:
http://www.lynchnet.com/ronnyr.htm
Script followed two characters, a sort of Frankenstein-esque human machine who would dance and sing when charged with electricity and a detective looking into a strange industrial town the movie was set in. Both versions of the script have drastic differences, and the movie has a lot of strange elements from the detective having a special power no one else can do by being able to put a finger on his nose while standing on one leg, to a scene of them hiding out in a woman's place and going to her basement and finding nightmare teens and a gruesome scene.
The elements that reflect strongest in this season are the strong themes the film had about electricity and gold. The current of electricity and the properties of electricity and strange machines were a big part of Ronnie Rocket, and gold was a reoccurring thing in the second script especially with the film even ending when the characters all float and ascend to a Golden Planet and Ronnie turns into a golden orb.
There's a few scenes in the new season that have HEAVILY reminded of Ronnie Rocket, and the tagline of the movie and how Lynch always described Ronnie Rocket, "The Absurd Mystery of The Strange Forces of Existence," is literally said by Albert in Part 3 of the new series.
-One Saliva Bubble
This was an early project by David Lynch and Mark Frost, it was their pitch for a tv series before Twin Peaks ended up being what they were going with. This one also has a screenplay available online, which you can read here:
http://www.lynchnet.com/osbscript.html
It's described as a comedy where a secret government project goes wrong, and several characters in a small town change identities. Not only is there some early Twin Peaks in the concept, but some of the stuff in the new season involving Dougie is very reminiscent of some parts of One Saliva Bubble.
-Woodcutters From Fiery Ships
This doesn't have a screenplay available, but it was a series being produced between Lynch and some Japanese anime studios, it was to be about a group of woodcutters on a ship and they smoke pipes and apparently look terrifying. There weren't a lot of details, but I'm sure you can begin to put together why I suspect this scrapped thing may have been pulled from in the new Twin peaks.
-Metamorphosis
Lynch wanted to do an adaption of Kafka with his own conventions, but it didn't go through for a few reasons. He wanted to create a believable and disgusting bug thing, Lynch never described the series in detail but mentioned he loved Kafka and had a script that was close to his heart. With Kafka popping up a few times this new season and the Frog-Bug we got in the new series with impressive effects when one of the things we know is Lynch thought they couldn't do what he wanted with the 'bug' back then for his script, I have a sneaking suspicion he's snuck some of this into the newest Twin Peaks too.
---
Those are four scrapped projects of his I have a feeling he's been finally able to explore some in the new season, though also of course there's things from their original Twin Peaks Season 3 ideas, and I also suspect maybe some scrapped things from the original Mulholland Drive concept when it was Twin Peaks related.