Sorry, I'm gonna rave about the EGM again:
One of the interesting things that the game lets you do is reinforce your ship with additional crew and equipment. You can choose a squadmate to be your XO (I chose Garrus), for example, which changes certain email stories and some scanning missions. You can also choose different senior officers, like a Marine Officer (Vega) and a chief engineer (take a wild guess). Although medical officer (default Chakwas) and supply officer (default Cortez) are there as well, you cannot choose who they are. A number of junior officer positions are present as well, but those cannot be changed.
Each of these options gives you some fan-written extended background and service history for each person.
The mod also lets you choose a ship marine detachment. As you progress throughout the story, you unlock options for larger detachments, from minimal and up. This doesn't change anything storywise or gameplay wise, but it does add a number of NPCs around the ship, including guards on certain locations (airlock, the cabin), as well as just hanging around the ship. It helps make the ship feel a bit less empty and more crowded.
There are some options that change your gameplay, too.
You can choose a medical team, which really is just one NPC, but the selection will give extremely minor bonuses to things like weapon damage, cooldown, and health. You get to choose between two humans, an asari, and a Salarian. Just like with the other NPCs the mod adds, they can be seen actually doing things. Sometimes just waiting outside the med lab on the crew deck, sometimes attending someone on one of the medical tables. But they're there, in addition to Chakwas.
As I mentioned in my previous post, you get to choose a chef. Only two are unlocked for me right now: a barman named Eli LeJeune who serves cajun food, been and "good times" and a chef named Keiko Hamada, who serves "high quality japanese food and a clean ship." Neither of these change the gameplay much, but the main bonus of a chef is that they feed your fish for you, and act as a complete replacement for the fish auto-feeder thing, which has been completely removed from the game. Like everyone else, they can actually be seen cooking and interacting with other NPCs, though as with all that the mod adds, there's no voice or interaction options. Who you choose also changes the models for the food that you see on the kitchen table, and on the table in the Cabin if you call your love interest up.
Once you get past Rannoch, you get two engineering crew slots. You get to choose two of six options: three Geth and three Quarians. These individuals have a greater effect on the Galaxy map gameplay loop, increasing the scanrange of the normandy's scanner, decreasing the rate at which you are detected, moving faster in system and in FTL, among other things. One of the NPCs is even familiar: Kenn'Raedor, the Quarian merchant on Omega.
You can add additional squadmembers, too. Assuming they survived, and there isn't a story reason for them to not be there, they can be added to a "standby" list which adds them to the squad list, and you can actually take them down on missions. Though, story missions may lock some of them from selection. For example, at least one "vanilla" squadmate is required when you do the bomb mission on Tuchanka, and once you finish the Tuchanka story arc, you loose access to Wrex. I presume all non-regular squadmates you can take with you in the Armax simulator from the Citadel DLC can be chosen at some point.
Additional equipment is neat, too.
Although your primary vehicle is locked, (the kodiak), you can choose a secondary vehicle that is also visible in the cargo bay towards the end, like a Mako for the dull, or a Hammerhead for the interesting. Different types of the same thing are available, too. Like anew IFV Mako, flying modern alliance colors. An option for the hydrolic flooring in the bay is added near Cortez's station that lowers or raises the flooring surrounding the vehicle.
You get a mechbay, too, allowing you to choose two types of mechs that are in the bay as well, like a YMIR mech and a Cat-6 Atlas. You can climb up a ladder to access a menu that can raise or lower them onto the ground, though they cannot be piloted. Just there for looks.
There's a Javelin missile battery as well, which takes up a lot of space but is still neat.
Oh, and perhaps the most impressive part: A fully functional shooting range, like on the Citadel Spectre offices. Complete with customizable targets, and the option for it to be casual (weapons but no armor) or formal (full gear).
All weapons that you unlock throughout the game are placed on a retractable and energy-shield protected weapons locker that can be slid out of the wall with a button press.
Speaking of the weapons, it adds every multiplayer DLC weapon and mod to the game.
There's an option to choose a Guard dog, though I haven't unlocked anyone other than Kei-9 right now.
Down in engineering, there's an engineering store menu that lets you access additional ship upgrades, like from ME2, that improve certain galaxy map gameplay elements, like the engineers. Faster speed, longer scanrange, and lesser detection from Reapers.
Oh and you can buy dextro chocolate for Tali, which shows up on the table in the cabin when you invite her up.
There's still a lot more that this mod enables, and I still haven't fully experienced it, but it is impressively integrated into the game. Sometimes I don't even realize it's something from the mod.
Edit:
It also adds another appearance outfit for Tali. Though I don't like the colors, I do like the Hood-Down option, and it's nonetheless impressive that it's been implemented into the game. For those wondering, the back of the head isn't actually modeled by default, and the modder hacked geometry from the Human helmets back there in order to make it work.