This is a project I've been doing on and off for a lot of months now. The idea is basically to extend the length of Skyrim's existing dungeons mainly through the addition of new cells. For example in Bleak Falls Barrow, after you slay the giant Frostbite Spider and cut down the dark elf, you'll find that the passage into the catacombs is suddenly blocked by debris, and instead you'll find a new hallway to your left leading into the new cell, leading down to a new canols section you have to go through, then up again to reach the catacombs section of the previous cell.
There are a couple of principles I try to adhere to for this:
-Difficulty with regards to enemies, puzzles, traps etc should be the same as the original dungeons, to ensure a seamless experience and compatibility with any rebalancing mods.
-Lighting, ambiance or any specific themes/quirks related to the original dungeons should carry over into the new cells and not deviate too much, again for a cohesive and seamless experience.
-Editing of the original cells should be minimal, only to connect and accomodate entry into the new cells.
-No editing to exteriors/worldspace.
I have already gone through several iterations and deleted entire cells that I thought weren't up to quality standards, and it will probably happen again in the future. I had started working on a new cell for Ustengrav with some added Greybeard themes but felt that it just didn't work. Lorewise I am unsure if the Greybeards actually built the place themselves or if it's just a dragon cult place retrofitted for their needs. I've also extended the tilesets with new models (both mod resources and retextured vanilla ones) for added flexibility, though it isn't heavily used yet.
So after scrapping Ustengrav I only have work done for Bleak Falls Barrow and Alftand so far. Main Quest dungeons are my biggest priority, with faction-related dungeons after that. Saarthal is probably next on my list. The cells are a pretty mixed bag in terms of how finished they are. I feel Alftand is the furthest even though it's the latest one I started just a few weeks ago. General ambiance and cluttering is far from finished, and I won't start on enemy placement/navmeshing until that is done.
General screenshot disclaimer: The only post-processing mods I have running for ingame screenshots is Dynavision and Climates of Tamriel (unsure if this one inherently edits interior lightning or on a per-cell basis). No ENB used. High resolution textures are used. My character is present to give a better sense of scale.
Bleak Falls Barrow
The overall themes here are a mix of caverns, natural overgrowth, bandit activity at the start and spider infestation.
http://imageshack.us/a/img402/1224/qv2a.jpg
http://imageshack.us/a/img703/2833/nhgo.jpg
http://imageshack.us/a/img59/6391/1i0m.jpg
http://imageshack.us/a/img833/643/gohk.jpg
Alftand
The overall themes here are frozen ruins, signs of expedition activity, and falmer activity later on.
http://imageshack.us/a/img62/9409/zhg7.jpg
http://imageshack.us/a/img521/7774/qcfk.jpg
http://imageshack.us/a/img833/9236/ycc5.jpg
http://imageshack.us/a/img822/234/w871.jpg
http://imageshack.us/a/img694/6953/czbe.jpg
http://imageshack.us/a/img826/3945/r28g.jpg
I expect this to be a very long term project that I'll just keep adding to over time. It'll probably be fit for initial release when I have 2-3 dungeons more or less finished. I sure wouldn't mind some help down the road though if there turns out to be interest.