There are loads of online tools to have fun with images in different ways like you can bloat, puncher images or you can improve images with some sane image editing tools. Here is a cool tool for some face flipping fun with images, PicHacks.
If you want to see how symmetrical your face is, use a forward facing picture with your head held perfectly straight. When placing the midline try to position it directly in the middle of the nose.
For funny results, experiment with different angles, tilted heads, and placing the midline in different places. Play around with it and have fun.