When to Add a Photo to Your Resume
If you're unsure about including a photo with your resume, I'd say you're probably better off not attaching one. Job applications almost never require pictures except in the fields of modeling and acting. In fact, pictures are usually inappropriate, especially when you're seeking an office position.
When it comes to public-facing jobs, though, I've found that resume photos can sometimes enhance people's chances of landing employment.
The Case Against Resume Photos
Why are photos with resumes so often unwelcome? Many companies believe that pictures are irrelevant, and they don't want their hiring managers to be subconsciously influenced by applicants' appearances. Moreover, a business might fear that a rejected candidate will accuse it of lookism, a bias that's based on people's looks.
In addition, you don't want to distract from your credentials. I know it's surprising, but the average hiring professional spends about six seconds making an initial decision about a resume, whether to set it aside or give it a closer look. Those individuals should be scanning your qualifications in that brief span of time, not studying your face or hair.
When Pictures Can Help
Sticking a photo to your resume may benefit you, however, if you're vying for a job where you'd interact with customers. Of course, bank tellers, food service providers, salespeople and many others routinely interface with the public.
Although employers shouldn't hire such people based on the way they look, your facial features or personal style could very well capture the interest of a hiring manager. I know that fact might seem unfair, but human nature can be shallow at times.
If you're going to send a picture, it should be one that a professional photographer took. Also, it ought to be an up-to-date head shot, and you should be dressed conservatively in it.
Finally, keep in mind that corporate rules and social mores change over time. Perhaps one day soon, we'll all be including our smiling faces in our job applications. Until then, if you're not seeking a public-facing position, I'd advise you to save your pictures for your social media pages.