I'm interested in this too. At the moment (and likely for quite a while going forward), we only have one "customer", and making my users enter "Customer name" on each login isn't great. I'd like to be able to make that a hidden field. Also, it would be nice to be able to add my organisation's logo on the login screen too.
Not sure if you've updated to 3.5 yet, but it looks like you can set a default customer name now, and even lock it so the field doesn't show up. Login as the SuperUser account, on the left side goto Settings -> Self Service Portal, then change the option of "Login customer preselection" to "Default customer" and select the customer name you want.
