I would suggest that you ask a friend to go with you and work as a team, introducing you to other persons. Another way to avoid ending up in a corner is to call people who might be interested in attending and make an appointment. If none of the above are possible, stay close to the entrance. That way, you will be able to watch all people as they come in.
Also, I would recommend writing down your "elevator speech" (a brief 2 minute description of who you are, what you do, and how that helps your customers). Practice it... in front of a mirror, and build up confidence.
On the other hand, I don´t think icebreakers should be rehearsed or prefabricated. If you have the latest news on the field, and current events, it would come natural to come up with an interesting question or remark. I regard icebreakers as very context-specific, depending on the event, guests, mood, the crowd´s culture and your networking motives and objectives. So, how do you come up with appropriate icebreakers? By doing. Eventually, they will flow.
