Google forms header image size
The header image should be at least 800px wide and 200px in height Click here to download a sample image of 800 x 200 If you have a larger image, you don’t have to bother cropping the image before uploading; Make use of the Google forms image cropper. (See below for more details) Adding the header image First, open the theme editor in Google forms Select Upload photo option Crop the image Update the color scheme to match the header image