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
