The main background image can be used two ways. The most versatile method for the background image for the Big Bob theme is it is used as a copy that sits behind all of your feed pages (like a posts page) and is set so that the entire image can be seen and any remaining negative space is filled in by your background color. It is the setting that occurs when the Background Copy control in the Background Image Section is set to ON.

If you’re not sure what to do, I’d recommend that you leave the Background Copy control in the ON position. Turning off this feature used to be the way background images were dealt with, but with the proliferation of mobile devices that don’t have the same compatibility as laptops and desktops, the old method has led to some frustrating results. Here’s why:

Mobile

The result of turning off the background image copy control is the background image is interpreted through classic css methodology. Mobile technology interprets this methodology in a manner that is distinct and arguably unfavorable.

Update: New controls have been added to the Big Bob theme. It is now feasible to create a mobile friendly fixed full screen background image. The remaining discussion is in reference to the classic methodology for creating fixed full screen background images that is still in common use and is far less versatile.

3/19/2021

There are several options you can choose from using the classic methodology. The options that tend to look best on desktops and laptops are when you choose to put the background image into a fixed and centered position. However, on mobile devices the response is that usually either the fixed position is turned off or the background image resizes every time the address bar shows or hides.

If you want to use the background image in this way then it is probably a good idea to turn off the background image on screen sizes that use mobile technology by adding the following code to the Additional CSS section:

If you choose to keep the background image for all devices, then you should definitely take the time to test it on different devices and make sure that you’re okay with how it looks. Whether you choose to use the image on mobile devices or not, you should definitely take the time to see how it fits to different screens and how it looks behind other images or videos.

You can read more about design advice for the Big Bob theme here.