It's hard to say.
In the top one, I see the corner of a wall in the yellow area.
The bottom one looks like stairs in the yellow, and that they definitely used flash.
I looked at the site they came from, and saw a few more that had different things that looked like motion blur of a light. I wonder if these could be shot with ambient light, long shutter and then flashed?
There is a lot of cool stuff on that blog. Too bad I can't read it.
I had a light leak on a camera, and it was pretty regular, and never contained imagery.