Using image files for your page background adds additional overhead for the HTML pages as they have to fetch the images via an explicit request and sometimes that can be time consuming which also impacts the performance of the entire web page.

See below for an example that creates a CSS property with a green background color. The second one creates a gradient CSS property whose color changes from blue to green with the width of the element to which it is applied.

.backgroundSingleColor {  background-color: green;}.backgroundGradientColors {  background: linear-gradient(blue, green);}