Great tips all-around. As my play sessions have hit 12 players, I think I might chime in here. A few tricks I've used, lately:
Parallel plot structure. Let the players split evenly (at 12, mine are split between 2 party cards) to investigate and explore. If a combat breaks out due to one sub-groups actions, fate will find the other group in a combat at well, with every player on the same initiative. Ultimately both groups should be working towards the same goal, but different specializations allow different routes. A simple tracker with 2 (or more) tokens can show the players how far along their subgroup is on that aspect of the plot.
Encourage competition. Encourage players to have personal goals aside from the obvious plot. This can be a headache for the GM, but it can also be an opportunity for players to interact with each other in-character while they are not the focus of the play. This sort of personal goal also allows you to place another player, not affected by the exchange, to be put in a charge of an NPC with a list of desires/information/characteristics and lets the two go off and still play, while not the focus. Just have the NPC player for scene check off what information they gave away so you can keep track of what players know. This requires book keeping between games, but allows players to stay entertained in-session.
DM Aid. In many cases, it helps to have a player as a DM aid for a social encounter. Usually, a player you speak of the game with outside of table hours. If they are willing to set their own character aside for a night or even just a scene it both removes the scale of the players and gives you a helping hand organizing. Most players love to have an idea of what's happening behind the screen. Be ready to compromise with this, however. The DM Aid needs be comfortable with what he says and not always look to you. When you can, make sure all players know that the DM Aid has all the power and say of the DM for purposes of that scene -- and make sure the Aid is comfortable/trustworthy not to derail anything.
Dice Roller App. There's a dice roller app. While I hate the idea of digital dice -- they're just not as visceral and satisfying as real dice -- they free up dice at the table and are available on any smart phone. This also has the downside of people having their phones out during a session, but overall it has benefitted my group.
Turns Outside Combat. Keep a table handy with all the character names. Choose a player to lead a scene and his character will take spotlight. He may invite other characters into the spotlight to participate and fully resolve a scene/sequence. Check them off for the "round." Find another player and do the same, ensuring every player has at least had the opportunity to be engaged in a scene before coming back around. It really helps to think of the WFRP timing system as "how long the camera is focused on your character before cutting away to another scene." Ensuing scenes acted out can be concurrent or sequential as the leading player desires.
Note Companions. In a large group, some players will group together more consistently than others. You can account for this during preparation, pre-empting how the group will split for discussions and small tasks.
1-Minute Hourglass. I got mine from a Yahtzee game. I keep it handy during combat, flipping it at the start of a player's turn. If the time runs out before they have acted at all, their turn in last. If it runs out after they've started, it costs them a maneuver. It helps keep combat moving and provides a visual queue to act rather than ponder.
In-fighting. I like it, but not every table does. I discourage directly killing within the party, but sharing misleading information is enjoyed. Keeping cards at 1 copy per playgroup helps encourage diversity of characters and also encourages in-fighting. After all, that thief has *all* the cool attacks and should he not be informed the museum is guarded by vicious dogs, there's a chance those cool cards will be freed up, soon.
Keywords. Be aware of all the characters' 4 keywords. Overlapping keywords quickly show you where the party specializes. A lot of Military means there should be more combat encounters to show off skills. A lot of Noble and Academic careers had best shun combat and shouldn't be forced into one.
Beware. One player's action can greatly affect the whole direction of the plot -- i.e. lighting Ascaffenberg's manor on fire. This is always a concern, but moreso with more players. It is one thing to derail a party of 4 and have 3 angry glares. It is another to anger 7 other players who each had a careful plan of action that will never be. Make sure you have a plan for plot derailment to ensure everyone can enjoy the session even with a radical change. If your players have communicated their upcoming goals, try to work in a way that they can still be accomplished with a few alterations.
Physical Props. These haven't been provided as well as they might in the books. But, having an illiterate character find a written note, and having to pass it to another PC to read aloud is a great way to add some immersion at the table and listening to the player-provided information is a nice way to engage everyone at the table, especially as they discuss the ramifications.
Finally, Seating. With a lot of players, I feel seating is an important aspect of ensuring a smooth session. Players who tend to be more involved in the game should be seated further away from the GM. If they are close to the GM, it becomes to easy for a discussion to happen that leaves out all the players at the table. Such exchanges are usually the best to keep a plot on track and won't have to be repeated after. Make sure to scatter system-knowledgable players so that when a question arises, a player can turn left or right to resolve an issue more quickly and without affected the flow of the session. Try to place any quiet players closer to remind you they are there. I find in the heat of a night, it's quite easy to skip over a player who is more timid and that's less fun for everyone involved.