Yay! Looking forward to this one. 
Me too! I've just been procrastinating about it and if I let myself do that it will never launch. So I'm going to get the game running, make sure the initial characters have enough to keep busy with for a while and then worry about introducing the metaplot, major npc's and extra player characters. Always better to improve a game in motion!
As it currently stands, there will be no overarching plot except that of Season 1. You can safely assume that the game will start amidst the developments of 'Midnight on the Firing Line'. Namely that raiders have been attacking near the station and that things have become tense on B5 following the confrontation between Londo and G'Kar over the Narn attack on Ragesh 3. The idea is that your characters are those 'extras' often seen in the series' backgrounds, or mentioned in passing. 'Someone reliable has passed me information...' etc. So you are still heroes, just not the Big Damn Heroes we meet in the tv show.
Anyone wanting in, let me know what you are interested in playing so I can ensure there is stuff to keep you entertained! Unless you want to be existing friends/relatives/contacts etc, I imagine that you will all start off doing individual things that will probably start to collide soon enough. If you have any questions, let me know and if the character concept you really want to play needs a higher starting level than first, let me know and I'll see what I can sort out for you!
The OOC thread for the game is located
here.