ProgressiveImage.js

import React from 'react-native'

var {
  Image,
  Animated,
  View
} = React

module.exports = React.createClass({
  getInitialState() {
    return {
      thumbnailOpacity: new Animated.Value(0),
    };
  },

  onLoad() {
    Animated.timing(this.state.thumbnailOpacity, {
      toValue: 0,
      duration: 250
    }).start();
  },

  onThumbnailLoad() {
    Animated.timing(this.state.thumbnailOpacity, {
      toValue: 1,
      duration: 250
    }).start();
  },

  render() {
    return (
      <View
        width={this.props.style.width}
        height={this.props.style.height}
        backgroundColor={'#CCC'}
      >
      <Animated.Image 
          resizeMode={'contain'}
          key={this.props.key} 
          style={[
            {
              position: 'absolute',
            },
            this.props.style
          ]}
          source={this.props.source}
          onLoad={this.onLoad} />
        <Animated.Image 
          resizeMode={'contain'}
          key={this.props.key} 
          style={[
            {
              opacity: this.state.thumbnailOpacity
            }, 
            this.props.style
          ]}
          source={this.props.thumbnail}
          onLoad={this.onThumbnailLoad} />
      </View>      
    )
  }
});

Update 2019, base on @alinz code
https://gist.github.com/DeVoresyah/d8888331509643edd612bca8a786bcb8