Dear Girl,
You say that he is "expecting a Pamela Lee look-alike?" Have you given him cause to believe that? If you haven't described your appearance much, showing him a picture will be easier. On the other hand, if you've portrayed yourself as a ravishing 5'10" red haired beauty with clear skin, admitting that you are not will be more difficult.
There are many ways you can handle the situation. The least desirable would be for you to cease all communication. You have established a rapport and it seems he cares about you. Disappearing without actually testing the strength of the relationship might be a foolish move, especially since you don't know how he will react.
Should your sin be one of omission, your task is fairly simple. Say that you have been hesitant about sending a picture because you don't feel that you are beautiful. Explain that you are really excited to meet him but worry that he won't like you after he sees your picture. Leave him a lot of room to interject "I like you for who you are and not for what you may look like." Then, hold him to it. Make sure you assure him that you don't think he makes decisions on looks alone. Even if it is true, no man wants to hear it. Send a picture and if he rejects you, find yourself someone who can accept you.
If you have been less than truthful with him about your appearance, telling him otherwise will be tricky. The best approach would be explaining that you were initially nervous about making a good impression, so you made your appearance something you thought he'd find attractive. Apologize for the deception, saying that you trust him enough to be yourself. Don't make him feel that you thought he was so shallow that he'd reject you based on looks alone. Send the picture after you get a response. He may feel hurt, betrayed, or played with, and you must accept responsibility for that. If he rejects, you have learned a lesson about truth and relationships. However, if he expresses interest, show him the picture.
As much as I would love to say that looks don't count at all, I can't lie. Many men, though, are attracted to women that aren't conventionally beautiful. It depends a lot on how you present yourself. Dress neatly, in flattering clothing, maintain excellent hygiene, accessorize tastefully, use some makeup, and hold yourself with pride. Get a picture of yourself in clothing that you know makes you look your best, even if you don't feel like a model. Take pride in your appearance and it will make a more positive impression. People are attracted to people who seem comfortable in their own skins and not based on societal standards of beauty. You've gotten him this far based on personality and intelligence. It is possible that you can turn this into a real-life relationship in spite of, or even because of, your appearance.
Sincerely,
Veronica