Good photo-collages are pretty easy to make, just contrasting things in ways that are quirky and eye-catching. But great photo-collages are hard, and when they work: woah.
Trash Riot is a prolific, science-fiction/retro-futuristic photo collage artist who makes their work available through Red Bubble (which sells them as posters, postcards, shirts, etc). I happened on Into the Eye yesterday on the Vault of the Atomic Age tumblr and was frozen in my chair by the beauty of it. When someone on Twitter later pointed me to the Redbubble site, I fell down a long and luxurious clickhole of aesthetic enjoyment.
Some of my favorites are below.
Trash Riot [Redbubble]