Hold Finger on touchscreen for 3 seconds. Note:This will put you in Edit Mode.
Touch the right hand corner icon which will look like this icon
Then Select either a color layout or your own photo
Go to the right hand corner and touch the camera
Now go to all or Photos and touch the photo you want
Now you will have a background on your vita page Note:Each Slide is custom to what you want. If you want each slide the same picture than you will have to do each individual slide.
To get out of Edit Mod, simply touch this icon.