https://botwiki.org/resource/tutorial/random-image-tweet/

random-image-tweet-attribution.js

/*
    A simple Twitter bot that posts random images.
    Tutorial: https://botwiki.org/resource/tutorial/random-image-tweet/
*/

const fs = require('fs'),
      path = require('path'),
      Twit = require('twit'),
      config = require(path.join(__dirname, 'config.js')),
      images = require(path.join(__dirname, 'images.js'));

/*
    Your config.js file should have the following format:

    const config = {
        consumer_key:         'XXXXX',
        consumer_secret:      'XXXXX',
        access_token:         'XXXXX',
        access_token_secret:  'XXXXX'
    }

    module.exports = config;

    Here's a tutorial on how to get the API keys: https://botwiki.org/resource/tutorial/how-to-create-a-twitter-app/

    And this is an example of an image.js file:

    const images = [
        { 
            file: '01.jpg',
            source: 'http://www.example.com/01.jpg'
        },
        { 
            file: '02.jpg',
            source: 'http://www.example.com/02.jpg'
        },
        { 
            file: '03.jpg',
            source: 'http://www.example.com/03.jpg'
        }
    ];

    module.exports = images;

*/

const T = new Twit(config);

const randomFromArray = (arr) => {
    /* Helper function for picking a random item from an array. */

    return arr[Math.floor(Math.random() * arr.length)];
}

const tweetRandomImage = () => {
    /* Then pick a random image from the images object. */

    const image = randomFromArray(images);
    console.log('opening an image...', image);

    const imagePath = path.join(__dirname, '/images/'+ image.file);
    const imageSource = image.source
    const imageData = fs.readFileSync(imagePath, { encoding: 'base64' });

    /* Upload the image to Twitter. */

    console.log('uploading an image...', imagePath);

    T.post('media/upload', { media_data: imageData }, function (err, data, response){
        if (err){
            console.log('error:', err);
        } else {
            /* Add image description. */
            
            const image = data;
            console.log('image uploaded, adding description...');

            T.post('media/metadata/create', {
                media_id: image.media_id_string,
                alt_text: {
                    text: 'Describe the image'
                }            
            }, (err, data, response) => {

                /* And finally, post a tweet with the image. */

                T.post('statuses/update', {
                    status: `Image source: ${ imageSource }`,
                    media_ids: [image.media_id_string]
                },
                (err, data, response) => {
                    if (err){
                        console.log('error:', err);
                    } else {
                        console.log('posted an image!');
                    }
                });
            });
        }
    });
}

setInterval(() => {
    tweetRandomImage();
}, 10000);

Thanks for this. I've created a Powershell script to help create the images.js file (because typing manually is tedious :) )
https://github.com/jimmyeao/twitterbotimgcreator

Nice, thank you for sharing!