What you wear below your shoulders doesn't matter - the picture should be primarily of your face, with neck and a bit of shoulders/upper chest. The background should be light and not have any writing/patterning. Whatever you wear should be pretty subtle and not distracting from your face. Given how little of your body is shown, even a t-shirt (not tank top) would be fine as long as it didn't have any writing/design on it. Below is similar to the photo I sent in, my hidden face has minimal makeup...no makeup, actually, and I am smiling. I'm wearing a plain T-shirt here, though you can't really tell.
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