«You never get a second chance to make a good first impression!»
That's the reason why it's important to make a neat appearance. If you come to take your CV picture, please pay attention to groomed hair, appropriate make-up and a bright, pleasant and natural facial expression.
Regarding clothing: Don't disguise, but please don't come in casual clothes with noticable patterns. Optimal is a button-up shirt with or without jacket, a blouse with or without blazer - in general, a plain and serious outfit. A neck tie is not necessary.