Not sure where you applied, but I would call the schools after you write one and ask if you wanted to send an LOCI, HOW should you send it - email, fax, snail mail, carrier pigeon, etc(trust me - kinda got burned by that this cycle).
As far as what to put in the letter, here are my 0L-not-of-my-lone-WL suggestions:
1. If the school didn't have a Why X school essay, include that and drop the names of the programs you're really interested in (and/or do your research on the professors and say why you'd like to work with them).
2. Mention if you've visited, have friends that attend, ANY connection to the campus that influenced your decision to apply and desire to attend if admitted.
3. Let them know you'd be willing to send additional documentation to support your app and that you'll call within a week to make sure the letter arrived promptly and discuss further measures.
Lastly, check you PMs - I'll send you a copy of mine