Factions

College of Winterhold

The college in the base game has one lesson and gives you one spell. Kill a few people and now your the headmaster. In LoreRim the college is now actually a college, where you have an Improved College Entry - Questline Tweaks  and a welcome gift. Not to mention you will get actual lessons on each school of magic thanks to College of Winterhold - Quest Expansion. Another much needed tweak was Choose Your Own Arch-Mage which allows you to rescind your position as Arch-Mage by selecting another member of the college to take up the mantle in your stead. 

The Companions

The companions have been tweaked with the mods Improved Companions - Questline Tweaks & Customizable Companions Questline Progression Requirements. 

Thse mods increase and allows to customize the number of radiant quests required for advancing in the Companions questline. Additionally you can actually back out of becoming a werewolf without leaving Skjor and Aela stuck in the Underforge forever, and various other tweaks for the Companions.

Thieves Guild

The thieves guild has been tweaked to with Less Tedious Thieves Guild. Remember that 125 job requirement for the full experience? Well, forget about that now.  This mod is a replacement script that brings the job requirements from 125 down to 25. Additionally, GG's Thieves Guild Headquarters improves the guild's home which gets better as you progress through the faction's main story. 

Dark Brotherhood

More contracts are availble with some of your most hated NPC named for death. However the biggest change comes on the starting quest Innocence Lost - Quest Expansion which provides new paths (both good and evil) to complete the first Dark Brotherhood quest. Additionally there is a big change with Unfaltered Virtue - A Penitus Oculatus Story which expands on the destroy the dark brotherhood path with its own storyline.

Bards College

In the base game, you walk in, asked to get a tome from a dungeon, bring it to solitude, start a festival and ta da your a bard who can't play an instrument and the college has 0 to offer. LoreRim fixes this by first of all, adding playable instruments. These also come with added benefits thanks to some perks in the speech skill tree and the bards college can actually teach you to play an instrument.

The college has several activities like Tome Trials - Bardic College Book Exams adds a unique mechanic to the Bards College, where you can take history exams and be graded for it. You can also compete with Aia Arria in the Bard's College to see who can memorize more poems with Poetic Duel. You can also take Typography Training in which you can go to Viarmo and ask him to teach you the Daedric alphabet. These activities reward you with a speech level increase.

After clearing  Dead Men's Respite a excavation team will appear with a repeatable quest to clear it out.