Ваше регулярное выражение неверно.Используйте внутренний Python urllib
для выполнения тяжеловесного поднятия вместо написания регулярных выражений, если вы не знакомы с ними.
Используйте что-то вроде этого (не проверено):
import re
import requests
from bs4 import BeautifulSoup
from urllib.parse import urlsplit # import this additional library
from os.path import basename # import this additional library
site = 'https://www.fotocommunity.de/natur/wolken/3144?sort=new'
response = requests.get(site)
soup = BeautifulSoup(response.text, 'html.parser')
images_div = soup.find(id=re.compile(r"fcx-gallery-\w+")) # focus on the div containing the images
if img_tags: # test if img_tags has any data
img_tags = images_div.find_all('img', {"data-src": True}) # get all the images in that div
urls = [img["data-src"] for img in img_tags] # grab sources from data-source
for url in urls:
filename = basename(urlsplit(url).path) # use this instead of a regex
with open(filename, 'wb') as f: # filename is now a string
if 'http' not in url:
# sometimes an image source can be relative
# if it is provide the base url which also happens
# to be the site variable atm.
url = '{}{}'.format(site, url)
response = requests.get(url)
f.write(response.content)