This is only available with a premium picnik account (it's only $25 for the whole year!)
Under the advanced tab there is a feature called Cloning.With the cloning feature you can select a point in the picture and copy it elsewhere on the image.
Here is the original image -
|Love you Uncle Larry but your bright yellow shirt has got to go...|
Here is the after.
|The trees look a little funny, but would you notice if you weren't looking for it?? I probably wouldn't.|
I think Picnik should hire me as an advertiser! :)