You play both Dead Space games at a time when the world has already gone to shit. Just about everyone's dead, and the place is a mess.
But in designing the world of Dead Space, it was handy to see what things were like before the bad stuff went down, when people were breathing and working and smiling and not crawling out of air vents trying to eat you.
These pieces, by artist Jason Courtney, are sometimes concerned with just that. Which might be why some of them don't look much like the Dead Space you know and love.
If that confuses you, don't worry, there are plenty of images that do look like Dead Space. You can tell because of all the blood and bits and junk.
You can see more of Jason's work at his personal site.