Assuming your ordinary niche blogger (no celebrity, no New York Times author, no one with a dedicated Wikipedia page):
Is there a way to have a photo next to his or her search result if he or she doesn't have a Google account?
Generally speaking, the mechanism used for attribution is not specific to Google accounts. It's just a rel="me" or rel="author" hyperlink somewhere in your articles, and you can list multiple source of profile data. (Which is generally a good idea for semantic web purposes. Take a look at the social links on my website for an example.)
That said, I believe Google Search only knows how to extract author bios from the Google Profile database. Personally, I don't think this is different than having to creating a Webmaster Tools account if you want to view your website data -- it provides an authoritative, user-editable source of biographical data for the system to use.
(If this was scraped from across the web for everyone, I could imagine some folks getting upset if the wrong information is picked up. Case in point: I remember a while back when somebody's Wikipedia article listed them as dead, and that information was automatically pulled into the Knowledge Graph. Oops.)
That said, I'm not on any of the teams involved in creating this, so take all this with a grain of salt.
