Most of the plotline elements are Thor's. I only kind of inserted some new stuff that I thought would make events more mysterious and less predictable. I appended the most new elements for the first part of the campaign, but there are also some stuff added to part two.
As for the missions, Thor had some pre-Beta missions but I added a bunch of stuff to them. Mission 1 and 2 were definitely started when I joined the staff (Summer 2003 or 2004 perhaps). All the other missions are mine, at least it is me who FREDded them (the mission outlines were already given). There are a few missions that I inserted into the plotline: the Abduction and the debis field mission, and maybe one other. Problem was that when I was in the last testing phase, I noticed a bunch of inconsistencies that came about due to the fact that sometimes even I did not know what I was doing. For example, one mission called the player's squad the 77th Blades but in the next one, they were called the 100-odd Silver Scythes. A lot of characters suddenly changed their ranks from mission to mission, too.
This whole Nyarlathotep involvement was my idea, though. No wonder I screwed up this "the Nyarlathotep was destroyed here, not there." thingy. But you know what? I'm glad this is the only Derelict-ITHOV inconsistency people have spotted so far.
Tables were almost finalized when I joined. I only added two or three new weapons and wrote a tech description for them. I think I also changed some of their values to better balance the weapons (the gatling gun, for example, was as rapid as a Maxim and dealt as much damage as a Kayser. Some would love to use such weapons, but I think more would dislike unbalanced weapons. I know this since it wasn't only one player who complained about the SOC fighters I made for RR for being too strong.
As for the models, I tried doing some modeling, but I found it a better idea just to use already existing material. I picked three of four models and made some new ships out of them. I hope to have given appropriate credit for them at the end of the campaign. These ships were the GTC Olympus (called the LPC Galleon in ITHOV), the GTI Bretonia, and the GTD Raynor. I also used the FS1 Apollo model.