Eh, I don't see why the Terror Track can't go down… If there are rules in the game, character abilities are made to break them, and that's a more thematic one, anyway (if something positive happens, the town feels less terrorized… maybe a store opens up again). But for something like that, I would make it difficult to accomplish, or couple it with a Herald or GOO that bumps up the Terror Track, so it's more of a push-pull kind of thing. Same thing with gates in stable areas… Never say never. Point is, I don't think there are any rules when it comes to breaking the rules… as long as it makes sense and there's a way to do it that works well enough. Don't do it for the sake of doing it, but there may be ways to mess with the system that are quite interesting and effective.
I totally agree, though, about making everything unique. As dense as the game already is, there are still many, many ways to create new abilities that haven't been used already. Sometimes I think there can't possibly be anything else that's new and interesting, but then an idea will come that opens up several new things. I'm always disappointed when I see a new investigator (or GOO) but they've just copied pre-existing abilities. Be creative!
I'm kind of in-between on the anachronism thing… By and large, yes, I think it makes sense to stick to the timeframe. All of the weapons and vehicles and items are meant to be 1920's, and it can seem a little weird to work outside of that. For example, Indiana Jones works perfectly well in that timeframe, but X-Files doesn't. That being said, X-Files was such a great fit in terms of the general setting (i.e., investigators trying to solve a paranormal case involving an alien/monster takeover), that I went ahead and did that, anyway, and I enjoy that variant a lot, some anachronism notwithstanding. But as Jake suggests, you can possibly find ways within the overarching scope of things to make weird things work, like a "rip in the fabric of space-time." And even then, I could see a computer as being some representation of a futuristic item, or an item that an advanced alien culture has developed which the humans of the 1920's need to figure out how to use when they find it.
Here's a thread on BGG with some notes on character creation, with comments from Kevin Wilson: http://www.boardgame...r-arkham-horror There are a lot of "rules" there that I would consider very strong, but not necessarily absolutes. Again… never say never. Most of those things are already programmed into Strange Eons.
For images, you'll want to find the link for the Spanish forum where they post images from CoC. Somewhere in this forum is the thread with that link. Tons of great images there, which are in the exact style of the game.