While Google makes themes available to style forms in Google Docs, there seems to be no provision for styling forms yourself.
I have a two-column layout and want the form on the right. There are various problems, such as the textarea overflowing the column. Since it's in an Iframe there's not way to wedge in a stylesheet or a jQuery/javascript fix.
The only suggestion I've found is grabbing the source of the iframe and dropping it into my own HTML, but this breaks the built-in validation and is too hack-ish.