Some Background on Backgrounds.

Managing file size in Revit must be a priority for large projects; else progress will slow to a painful pace. There are many places to manage, but for the MEP engineer, the first place to start is with the background files. The architect's files that are linked in as backgrounds are really just there for the floor plan, and model coordination. It would be fair to say that everything in the linked file is overhead for the performance of your model. So make it a minimal as possible. Delete as much out of it as you quickly can. Every byte of information you remove, saves time for each person opening the project. Delete out all of the sheets, every one of them. You're not linking to their sheets, so you're not using them. Delete them. Delete the schedules, the legends, the sections, and elevations too! If you're not linking to the view, delete it. Purge the heck out of it, till there is nothing left to purge. Obviously don't get too carried away. Make sure you don't really need something before you delete it. But the more you can delete, the better off everyone will be. The only things I usually keep in my background files are overall floor plans and RCP plans.

Don't invest too much time into this process. I have heard of people spending an hour or more deleting stuff out. Make it a quick process, where you get the most bang for your time. If you have the resources, write a script to delete stuff you know you won't use quickly. Get the process down to 5 minutes or less.  I usually get Architectural backgrounds starting around 125 megs, and can reduce it to about 54 megs.  Your mileage may vary.