Little script for procedural generating parallax background sprite. I use it for generating a lot of little stars. You can adjust size of the image, amount of stars, star sample sprite, deviation in size (don't set 100%).

star generator.py

from PIL import Image
from random import randint
import math


def distance(a, b):
    return math.sqrt(math.pow(b[0] - a[0], 2) + math.pow(b[1] - a[0], 2))


def is_near_other_star(star, stars, min_dist):
    for _star in stars:
        if distance(_star, star) <= min_dist:
            return True
    return False


def create_star(star_size, img_size):
    return (randint(star_size[0] / 2, img_size[0] - star_size[0] / 2), randint(star_size[1] / 2, img_size[1] - star_size[1] / 2))


def deviate_size(original_size, deviation):
    bonus_size = float(randint(0, deviation)) / 100 * randint(-1, 1)
    x = original_size[0] + (original_size[0] * bonus_size)
    y = original_size[1] + (original_size[1] * bonus_size)
    return (int(x), int(y))


if __name__ == '__main__':
    created_stars = []

    img = Image.open(input('File name: '))
    size = tuple([int(x) for x in input('WxH: ').split('x')])
    amount = int(input('Amount of stars: '))
    min_distance = int(input('Minimum distance: '))
    deviation = int(input('Size deviation (in %): '))

    for i in range(amount):
        new_star = create_star(img.size, size)
        while is_near_other_star(new_star, created_stars, min_distance):
            new_star = create_star(img.size, size)
        created_stars.append(
            new_star
        )

    bg = Image.new('RGBA', size, (0, 0, 0, 0))
    for star in created_stars:
        bg.paste(img.resize(deviate_size(img.size, deviation)), star)
    bg.save('result.png', quality=95)