How the initial position of a background image can be modified?

The background-position CSS property sets the initial position for each background image. The position is relative to the position layer set by background-origin.

/* Keyword values */
background-position: top;
background-position: bottom;
background-position: left;
background-position: right;
background-position: center;

background-position: center right; /* pairs */

/* <percentage> values */
background-position: 25% 75%;

/* <length> values (horizontal | vertical) */
background-position: 0 0;
background-position: 1cm 2cm;
background-position: 10ch 8em;

/* Multiple images */
background-position: 0 0, center;

/* Edge offsets values */
background-position: bottom 10px right 20px;
background-position: right 3em bottom 10px;
background-position: bottom 10px right;
background-position: top right 10px;

/* Global values */
background-position: inherit;
background-position: initial;
background-position: unset;

Source: https://developer.mozilla.org/en-US/docs/Web/CSS/background-position