Your friends want you to have fun. You don't need to think deep down about your looks. Some people are worried about their looks to get into parties, and you are invited to go to one. If you get a picture taken of you, so what? Don't use that picture as a nasty reminder, but use the picture as a great reminder of how great your friends were for taking you to an event. You have your feet and your cell phone too. You can leave at anytime you want to. No need to worry. I hope you have fun at the party.