Even if the temperature where you live never drops below freezing, you can still have a row of frosty icicles -- inside, no less!
Cut white glitter felt into a strip 6 1/2 inches wide and as long as your shelf. On the non-glittery side, draw long, pointy icicles with a pencil and cut them out, leaving a border of 1 1/2 inches on the top edge.
Cut a strip of white paper about 4 inches wide and as long as your shelf (tape multiple pieces of paper together as needed). Fold over 1/2-inch of one edge, then join the felt piece and the folded paper with a glue stick as shown.
Clear a shelf, lay the paper on it so that the icicles hang down, and replace the objects to keep the shelfsicles in place.