Morrowind Wallpapers and Loading Screens. Yeah, I know: catchy title. But still, it has 66 splash screens (the kind that show while Morrowind's loading) that make the stuff that came with the original program look like the efforts of a 5-year-old. (And a 5-year-old who's clearly going to become a conceptual artist, at that.) Beautiful images by day and night of many areas, shrines, and cities--with more on the way. Nice font, too. You'll need an image program like IrfanView (free, by the way) to resave the each of the files as 1024 x 1024 and in targa format, but I did that in less than 15 minutes.
Magistrate's Mage Guild Rewards 2.0. There are already a few mods that provide reward incentives to reaching the top of a guild or house--Dracandros' Voice being probably the best--but this one is more detailed. It adds a teleport room that lets you move quickly to any of the Mage Guilds for free, and a second-in-command who buys and sells magical supplies, enchants, offers a few spells, and even repairs items. If you make from Master Wizard to Archmage, you also gain access to a bedroom/study with good chest space, and a room with a giant crystal that lets you control the weather. Very nice.
Abu's Retreat. My favorite house mod: lots of plants, lights, books and wall hangings really make this one seem lived in, rather than simply a warehouse. Has a nice alchemy lab (all ingredient jars, including Sri's), a very attractive kitchen area, a decent display room, and a small but great greenhouse that simulates the effect of daylight or night through the glass roof. Really kinda small, but that's the way I prefer my houses in Morrowind.
The Muck Shovel of Vivec. A professionally done quest with a side dish of humor--something you seldom see in Morrowind mods.
Erenguard Mines. A strategy add-on: you can buy the services of miners, guards, stock up on food, drink, picks, etc, and need to find the right balance to keep everyone happy and everything profitable. Nicely done.
Enchanted Icon Selection. One of those tiny ease-of-use mods I love. This one gets rid of the horrible enchantment icons that cover whatever you're looking at, and replace 'em with a selection of very easy to see symbols that only affect a small portion of the icon surface. I use the gold star one, but it's up to you.
Dodge. If you're playing a pure mage, get this. It adds a dodge bonus based on your unarmored skill, effectively making unarmored a reasonable choice instead of a deathwish.
Windows Glow. Adds a light source to external windows, making them glow at night. There are a range of colors to choose from. Really nice effect.
Sorefoot Enterprizes. The Silt Strider business is expanding, with new locations, buildings, NPCs, and quests. Good writing, some truly creative questing, as well.