anti-photobomb 

Someone who should appear in a picture whose face is mysteriously absent, often by being misplaced behind another person's head.

The opposite of a photobomb. Whereas a photobomb involves exploding into a photo, an anti-photobomb is more of an implosion, except with the effect of no one noticing.

The introvert's photobomb.

Friend: Hey, here's a picture of all of us. But where's Tim? Maybe that's him--the one who turned last minute?

You: Yeah, that's him. He's shy, you know, so he anti-photobombed.

anti-photobomb by hoochiscraaazy September 26, 2010

reverse photobomb 

When you see something so weird or amusing you have to bomb your own photo to get the goods. The opposite of a photobomb, where someone jumps in at the last second to be in it.

snapping that photo of the elephants boning behind you. No one wants to admit they were looking, but now you have photographic proof! reverse photobomb!

reverse photobomb by tfghost November 5, 2009

Reverse Photobomb 

Grabbing someone who is meant to be the centre of attention in a photograph out of the shot at the last second, meaning the photograph is minus a person that is meant to be snapped, as opposed to 'photobombing', where someone not meant to be in a picture gets themselves into it.

The grabbing out is preferably done with a hooked walking cane, in true cartoon fashion.

Chuck: "Dude, Carl is so up his own ass, go and reverse photobomb him out of that shot with all those dames."

Barry: "Let me grab my cane..."

Reverse Photobomb by Rick Felatio June 19, 2013

Unintentional Photobomb

When you accidentally manage to get in someone else's photo. (And it ends up biting you in the ass later. i.e. Getting caught cheating on your partner or otherwise lying to them about where you were and/or who you were with.

Me: "I was looking at cool event photos from a few years ago, and saw my husbands lying ass drinking with a buddy and two chicks. He said his ass was going for a ride on his motorcycle that day!!"

Friend: "Unintentional photobomb... Does it every time."

Unintentional Photobomb by Sporadiclove February 28, 2015

photobombing 

Intentionally posing in other people's photos, for a later surprise.
Usually people making funny faces in the background, without the knowledge of the main subjects of the photo.

Jim is always photobombing, he messed ups some of the best photos from the wedding.

photobombing by U8IK May 6, 2008

Photobooth 

An alternative which is used by many people who do not own phones to take selfies and to post them on social media.

"Guys check out my new instagram post."
"Ew you took it on photobooth?"
"No I didn't..."

Photobooth by xmancrushmonday November 28, 2016

PhotoZombing 

A subset of Photobombing where someone deliberately appears in the background of other people's photos while adopting a zombie-like pose.

Man did you see James picture on the beach, there's some guy photozombing in the background like totally night of the living dead.

PhotoZombing by Groaning Required September 21, 2011