I'm a homeroom mom so I recently searched the net for ideas. I found two that I liked...
One was basically a shoebox covered in plain pink or white paper and then a cardboard cutout of a teddybear, monkey or whatever you like attached to the back of it, with paper arms that come around form the back and attach with their hands holding a heart on the front of the box, like it was hugging the box. The animal cut-outs were accented by heart-shaped inner ears, a heart nose, etc. There was a basic slit in the top of the box to insert valentines.
The other idea (the one we're goigngmake as a class) is to take a gift bag with handles, attach a large heart to the front and cut a large "mouth" through the heart and bag. Add large googly eyes above the mouth and accordian-fold arms and legs with hands and feet at each end. (it reminded me of one of those large mylar baloons you can buy with the arms & legs, or even Spongebob)
I don't imagine I can post the images as I don't remember where I got them, but if you are interested in a pic of eaither, PM me.