Styles

const React = require('react-native');

const {Dimensions} = React;

const deviceHeight = Dimensions.get('window').height;

const deviceWidth = Dimensions.get('window').width;

const {StyleSheet} = React;

export default{
    container: {
        backgroundColor: '#FBFAFA',
    },
    background: {
        flex: 1,
        width: deviceWidth-40,
        alignSelf: "stretch",
        justifyContent: "center",
        // alignItems: "center",
        resizeMode: 'contain',
        height: deviceWidth-40,
        margin: 20
    }
};

Component

import styles from "./styles";

...
render () {
    return (
      <Container style={styles.container}>
       <Header style={{ backgroundColor: '#F8F8F8', 
                        paddingBottom: 20, 
                        paddingTop: 30, 
                        borderBottomWidth: 0,
                        elevation:0
                     }}>
       </Header>
      </Container>
    )
  }