sickkittens - Your index should be your warning page, so a warning to surfers that it's an adult site is necessary (in my book anyway)
As far as links, this is usually where people put up their recips as well as a few ads (based on the # of ads the sites you're submitting to allows)
The rest of the design of the index page is pretty much up to you
lagwagon - I prefer standard/basic free sites to the flashy graphic intense ones, but I of course list both