Re: Changing the main menu character?
wisecode almost got it right, the correct command would be "map_background", which loads the map while still showing the menu items on top of it.
This means that you can right click SiN:Emergence in your Steam games list, choose properties, click "Set launch options" and write "+map_background background01" (without the quotes) if you only want Jessica on your menu.
There are actually backgrounds for 01-06, but it seems that both 05 and 06 show Elexis (altough I can almost swear that it showed me Jessica the first time I loaded 05... weird).
If you really want some control, you could make yourself several shortcuts to start Emergence, each with a different character on the menu. Just ask Steam to create a desktop shortcut for you, and then edit the target line by appending the "+map_background background01", then make another pointing to background02 and so on.