Larger images are available.

What do you mean? I'm not really familiar with submitting pictures, what are the requirements? Please help.

I couldn't quite go into a lot of detail when I was typing that yesterday, sorry.

When uploading an image, the below text is included:

The better and larger the image, the better the eventual cut-out will be. If you're having difficulties in finding a good source image, have a look in this thread for some hints and tips on how and where to find the best possible sources for your requests. 

A simple Google Image search threw up larger sources than the one you requested, in fact, for example.