I can't provide if this is 'acceptable', but can only provide my preference-- and it is just mine alone.
- A headshot that is less austere: not a toothy grin, but somewhat of a smile.
- Would prefer a dress shirt, open at the collar, in either white or a soft color. The idea is a business-casual attire, in a softer look.
Think the head shot should leave the impression of a 'go-getter' and "I would really like him for a student" impression.
Again, IMHO.