For the PBW file library? No, there shouldn't be any problem. What are you calling big?

If it's bigger then 5MB all I ask is that you put something in the comments to that effect so people who try to download it can get an idea how long it's going to take.
We've never had to put any kind of restricitons on mods for the PBW library. I even tried to get Hadrian to post his UM1 there, and it was what 15MB? I can't remember now.
We have gigabytes of space available. If it starts filling up I can always go back and delete old Versions. As it is now there are some mods with several Versions on it.
Geoschmo