Clean the bottles with soap and water. If the label's adhesive does not come off, try using a product like Goof Off or Goo Gone. Let bottles dry completely, inside and out. (Sometimes a paper towel stuck in the top helps dry inside out.)
Carefully roll your photo (paper copies work best) and slide it into the bottle. Use the paintbrush or pencil eraser to push the picture down and try to open it up a little. To add to the fun, write a note on a piece of paper or on a brown paper bag to add to the bottle.
Find a cork or stopper that will fit snugly in the bottle. Use a hot-glue gun to attach a shell or a favorite trinket to the top of the cork. Place the cork into the bottle and make sure it stays put. To add some depth and character to the piece, wrap the top of the bottle in decorative wire, costume jewelry or anything personal.