The digital camera is not a viewing device. The LCD is primarily for checking the pictures the camera took. Most digital cameras do not recognize pictures taken by other cameras or pictures manipulated through a graphics program in the computer.
You can copy and store pictures from other sources to the memory card of your camera but do not expect it to show up in Preview Mode. The pictures are there, only not visible. You can use the card to carry other files, even non-photo or video ones and transfer them to another computer. If you bring the memory card to a photo printing shop, they will be able to get the other pictures and print them.
Now you know!