On September 2, 2014 Google announced custom themes. See [Your forms, your way] (http://googledrive.blogspot.mx/2014/09/custom-forms-themes.html)

The steps from the related help article Add a theme to a form - Docs Editors Help are the following:

Create a custom theme
If you want even more control over how your form looks, you can create your own custom theme.

1. Open the form.
2. Click Change theme in the toolbar.
3. Find one of the existing templates in the panel on the right to use as a starting point and click Customize under the name of that template.
4. Select a section of the form in the panel on the right to begin editing that section. Some of the options you can customize include:

• Adding custom images to the header and the page background
• Choosing font, font size, font color, and paragraph alignment for the form text
• Choosing a color for the form and page backgrounds

On September 2, 2014 Google announced custom themes. See Your forms, your way post on Google Drive blog.

The steps from the related help article Add a theme to a form - Docs Editors Help are the following:

Create a custom theme
If you want even more control over how your form looks, you can create your own custom theme.

1. Open the form.
2. Click Change theme in the toolbar.
3. Find one of the existing templates in the panel on the right to use as a starting point and click Customize under the name of that template.
4. Select a section of the form in the panel on the right to begin editing that section. Some of the options you can customize include:

• Adding custom images to the header and the page background
• Choosing font, font size, font color, and paragraph alignment for the form text
• Choosing a color for the form and page backgrounds