Disclaimer: This will not add any fantastic NPCs with unique dialogues, or quests. It will be vanilla flavored which suits my needs just fine - I, personally, would not stroll into a random town and start harassing the farmer's son about his life's story. This will also not touch any of the major towns (except perhaps an option file which will add walls to Dawnstar and Falkreath).
Take One; Whiterun Hold
First up is Rorikstead, when I first entered the town it just screamed "MANOR". Traditionally, many manors had strong walls, a contingent of it's own guard, farms, a blacksmith, a stable, and in many cases stone walls to defend the landed knight. Manors did not feature a keep, to the best of my knowledge. Since this is Elder Scrolls I have also added a general store, for the well being of travelers. This one is almost done, all that's left to do is whip up some basic NPCs, increase the amount of animals and vegetables, add clutter, and give it a quick walk-through to make sure the navmesh behaves properly.
Note: I will be creating a path for this mod http://skyrim.nexusmods.com/downloads/file.php?id=17865 (Highland Milk Farm) before proceeding onto Riverwood. After getting in contact with it's respective author, of course.
Riverwood: While Rorikstead may have supplied food and fur for the hold, Riverwood serves a slightly less but still vital purpose - metal. A number of ore veins and mines surround Riverwood and I will create a few more for the purpose of realism. It will also be shown to reflect Riverwood's value from the game (deer, fish and rabbit) it brings in. It will not add heavy stone walls as I feel Riverwood is not a manor, but a town, and the NPCs in game state that the town is unwalled. It will, however, feature a palisade (in a similar vein as the orc strongolds), a small additional farmhouse for a number of guards (probably 4) to dwell there permanently, and the guards sent by Irilieth early on the main quest will be changed into Whiterun "Rangers" who will take advantage of some of the new defensive structures and make defending the down from dragons more practical. The Dragonborn is not omnipresent (at least mine is not).
Suggestions, comments and questions are welcome. As well as constructive criticism.
Screens of Rorikstead:
From the Reach - http://imageshack.us/photo/my-images/69/2012053000001.jpg/
The New General Store - http://imageshack.us/f/84/2012053000002.jpg/
Guard House - http://imageshack.us/f/403/2012053000003.jpg/
Blacksmith - http://imageshack.us/f/207/2012053000004w.jpg/
Pride of the Hold - http://imageshack.us/f/254/2012053000005.jpg/
View of the low, but effective, walls - http://imageshack.us/f/607/2012053000006.jpg/
From Whiterun - http://imageshack.us/f/820/2012053000007.jpg/ (The lamp post clipping is from Claralux, a mod I highly recommend)

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