So first, what do you mean by "one of your teams on the organization?" Who are you expecting to answer this question?
Next, you can't change the stamp size. The size of the stamp is the size of the page that defines the stamp.
However, you can create the appearance of a stamp that changes size. This is a somewhat tricky process. The key is to use a form field as the background, because field properties can be changed during stamp script execution.