in order to get wallpaper 142, you need the child effect and you must go the new dream beach area. First off, you have enter the small house with the dream beach and use the child effect on the demon girl sitting inside and have her exit the house. You follow her outside till she disappears in the middle of the beach with her laugh. After which you return to house to find her missing. This is will trigger the wallpaper. Just remember as far .097a in concerned, this wallpaper is not viewable within the game bacause when you are looking at it in the wallpaper gallery it crashes the game.
As for wallpaper 140, I was able to glean from the japanese wiki that it requires all the kura puzzles to be collected. I could be wrong. Just a suggestion regarding this wallpaper, I would appreciate if anyone would set up a similar guide for collecting all the kura puzzles as wallpaper guide. I only need to find puzzles 31,41, and 42 for completion.