140px width by 140px height (NationBuilder will automatically resize a photo down to these proportions upon image upload. Just make sure the image is a square.)
Featured Content Sliders:
660px-960px width by 250px height (660px if in the left column, anywhere between 660px to 960px if the slider spans the entire page width)
Header Image (banner):
960px width by 150px height (learn more about resizing your header image)
Background image for Focus theme:
1024px width by 768px height
Recommended image sizes are different for the Busy Biz, Civitas, and Victory themes. Learn more about these themes on our public theme guidelines page.
Note: the pixel dimensions listed above assume changes have not been made to the template widths of $page_width, $left_column_width, and $right_column_width in theme.scss. Your can disregard this note if you aren't using a custom theme.