In fact, it is a bug in 7-Zip. As program's author Igor Pavlov explains, the following happens when Windows Photo Viewer is set as default image viewer in Windows:
The Program1 (some photo file handler) calls another Program2 (windows photo viewer) and closes Program1. But 7-Zip waits only Program1. So it deletes image from temp folder. I plan to fix that problem in future.
The problem still exists in latest stable 7-Zip 9.20, though I didn't check if it is fixed in latest alpha.
There is a not-so-difficult workaround: use alternative image viewer as your default one. Personally, I use FastStone, but XnView etc. should be fine too.