Hey Amy,
How are things down under?
I'm working on the same thing at the moment. Seems ESRI is really pushing layer files and layer package files to be used with AGX ...and probably rightly so to be honest. However, I'm in a similar situation where I have a lot of users utilizing AGX that don't necessarily have (or want) a lot of background in GIS.
I found an XML file in the styles directory that you can edit by hand with a text editor like Notepad. The tricky thing with this method is that it can be fairly labor intensive and you'll need to drop PNG files into the SymbolImages directory if you want to use custom images, etc. I wound up literally building a couple of hundred images with Adobe Fireworks and simply referencing them in the XML (I have to laugh a little just thinking about that!).
Another option I'm playing around with today is building a Gallery Add-In with MS Visual Studio and the AGX Software Developers Kit. With the SDK install, ESRI was kind enough to drop in some samples for developers (and amateurs like me). There's also a free ESRI training course out there called Extending ArcGISExplorer, or something along those lines that was pretty good.
If you make any progress, or would like to swap some code, just give me a shout.
Nick
Geospatial Intelligence Analyst
Washington, D.C.
