Can photographs of people be considered idols? Is it the kavanot that the viewer ascribes that is important or is it inherent in a 2D image of a face?
A photograph can be considered an idol if there's someone who's worshipped it as one, same as most anything else. If it was made by a (halachically non-Jewish) religionist as an idol of his religion's, it's considered such even before it's worshipped (Shulchan Aruch, YD 139:1). Therefore, certain pictures should be assumed to be idols absent knowledge to the contrary (SA 141:1–3); which pictures that rule applies to depends on the time and place (Shach 141:17, Beur Hag'ra :18). But there's nothing inherent in photographs of people that makes them all into idols. As always, for practical questions, contact your rabbi rather than relying on what you read here.