Most people's pictures on dating sites are only of them. It makes sense: if you're on the site, the point is for people to date you, not your friends. Also, I've always found it kind of rude to put pictures of friends/family up on dating sites without their permission, since they may not want their pictures up on the internet like that.
Now, on to your question: I think that having a social life is important, but I think that having a life is far and away more important. You just need to have something going on in your life, so that you stay busy even when you aren't with your partner. In my case for example, I hardly have any close friends, and my social life mostly involves a night out every now and then with some coworkers. However, I keep myself very busy with my hobbies - exploring the outdoors, visiting new places, cooking, etc. I have never felt that my lack of a social life has inhibited me with dating at all, but I think that if I didn't have an active life full of hobbies and activities, I think that it would significantly hinder me. Plus, having a lot of things going on gives you plenty of interesting conversation material to grab a potential partner's interest.