Personally, I have no trouble with all the ages being found in the Nexus - that avoids the need to design a gigantic, continually expanding library building for the books, or worse, making such a library AND trying to fit it into Relto somehow.
There are about 90 fan ages now. And that's just the start.
What I'd personally want more than a library and lots of shelves, is (in the Nexus) to have some sort of good sorting method for the fan ages, something which helps you find the ages you're looking for.
Wouldn't it be great to be able to sort through fan ages by looking at:
-Name
-Author(s)
-Date released
-Rating
-Images
...and so on?
As for quality, I know, the ages we've seen thus far are mostly pretty mediocre. That said, most systems of user-created content start that way. In any game, usually the first wave of mods and levels are pretty bad. As the fan artists gain experience with the tools, and the tools are improved, and the artists are given enough time to complete better, bigger projects, then a fanbase can produce great things.
The ages that turn out well are usually ones that take a while to finish. It takes thousands of hours, potentially, to construct an age that looks as good, and works as well, as the ones Cyan Worlds makes. They had a team of 37 people working for a year on MO:UL, and that's what it took to make the content they released. So, let's put it this way - to make a fan-created equivalent of Eder Delin, you need something like five skilled/talented fans working on it for a year, full-time. But since we're doing it as a hobby, it takes longer - so imagine that our hypothetical "Cyan-quality age" takes 3 years of part-time work from a team of seven fans, just to get one excellent quality (but fairly small) age made.
The good news is that such quality projects ARE in production. Eh'ko is not the only example.
Breldur looks absolutely stunning, Yinfara and some other GoW group projects show a lot of promise, Keith Lord's work is really good, the stuff that Subterranean Restorations is doing - it's kind of secretive and I can't say much, but I've seen some of their work and it's starting to look really impressive. They have great concept art and they're slowly cobbling together detailed environments from it.
For my part, I'm trying to create something of quality too, with my temple environment. It's nowhere near complete yet, but when it is, I think/hope it'll turn out well.
The GoW forums have 778 members. That's a big group of fans. We have hundreds of people working on fan ages right now, gaining skill in their craft, a few of them nearing professional quality in their work, and I'm sure better content will be released during the next year or two as some of the more ambitious, longer, better-quality projects are completed.