Here are some examples of the same photo altered using some of Picnik's more "normal" photo effects:
Okay, so those two weren't so normal, but they are cool, right? And the Duo-Tone one lets you choose the two colors you want to use.
And my favorite:
I used this a while back for the photographs on this layout:
There are tons more photo effects and frames you can add, in addition to the regular photo-editing features, like cropping, resizing, brightening, fixing red-eye, and many more.
So what are you waiting for? Go zombify yourself!