I don't know how to do it in webshots, but in PhotoPoint I either resize it using their editing tools, or I take a picture where the dog is further away and crop every thing else out of it so what is left is the "little dog". Webshots has a free editing tool that you can download called "My Photo Assistant" but I couldn't get the crop tool to work on my computer.
Sorry this isn't any help, but maybe My Photo Assistant will work for you.