If you're looking for more scenarios, graphics, scripts, and whatnot for BoA, try some of these sites.
If you're looking for other designers' websites or other BoA related sites, Lord Grimm has a large and growing list of them.
-Link Library
For scenarios, Tyranicus has compiled all those existing into a database. Of course, you can also find them at the Official Blades of Avernum website.
-The BoA Scenario Database
-Official BoA Scenarios Page
If you want more graphics, try looking in the Louvre. If you don't find what you want there, track down some designers' websites.
-The Louvre
Look in the Lyceum's Codex for some revolutionary new scripts. Not sure how much longer that's gonna be active, but see it while it lasts!
-The Codex
The latest edition to Blades references is here as well. The Blades Forge, brainchild of Arancaytar, combines scripts, graphics, scenarios, and more into a nice and easy-to-navigate database. Check it out; it's useful.
-The Blades Forge
If you're a new designer, you should join the community *before* publishing any scenarios. That way you can ask questions, seek out the general consensus of opinions, and generally get to know the people you'll be distributing works to. I recommend the Spiderweb Software Boards, specifically the ones called Blades of Avernum and Blades of Avernum Editor. Oh, and uh… leave your sanity at the door.
-Spiderweb Software Boards
I also recommend the Shadow Vale, hosted by Tyranicus. It's less active, but generally more personal than the official SW boards.
-Shadow Vale Forums