Downloading images from URLs
Notes about your code


You can also simplify the way you look for the links to follow:

for link in soup.select("a[href]"):
    downloadImages(link["href"], level - 1)


Here, we are enforcing the a elements to have href values, not checking for elements to be found (since the loop body would just not be executed in this case).
As far as managing the urls you've already visited:


don't use globals
use a set instead of a list for faster lookups

It's also a good practice to always specify the parser BeautifulSoup uses under-the-hood:

soup = BeautifulSoup(urlContent, "lxml")  
# or soup = BeautifulSoup(urlContent, "html.parser")
# or soup = BeautifulSoup(urlContent, "html5lib")

follow PEP8 recommendations - specifically, naming is agreed to be in lower_case_with_underscores format, not camelCase
no need to join the urlContent - simply pass urlContent to BeautifulSoup


Alternative solution

I would implement it this way:

try:
    from urlparse import urljoin
except ImportError:
    from urllib.parse import urljoin

import requests
from bs4 import BeautifulSoup


class Scraper:
    def __init__(self):
        self.visited = set()
        self.session = requests.Session()
        self.session.headers = {"User-Agent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.109 Safari/537.36"}

        requests.packages.urllib3.disable_warnings()  # turn off SSL warnings

    def visit_url(self, url, level):
        print(url)
        if url in self.visited:
            return

        self.visited.add(url)

        content = self.session.get(url, verify=False).content
        soup = BeautifulSoup(content, "lxml")

        for img in soup.select("img[src]"):
            image_url = img["src"]
            if not image_url.startswith(("data:image", "javascript")):
                self.download_image(urljoin(url, image_url))

        if level &gt; 0:
            for link in soup.select("a[href]"):
                self.visit_url(urljoin(url, link["href"]), level - 1)

    def download_image(self, image_url):
        local_filename = image_url.split('/')[-1].split("?")[0]

        r = self.session.get(image_url, stream=True, verify=False)
        with open(local_filename, 'wb') as f:
            for chunk in r.iter_content(chunk_size=1024):
                f.write(chunk)


if __name__ == '__main__':
    scraper = Scraper()
    scraper.visit_url('http://www.yahoo.com', 1)


Aside from things mentioned above, here are some other applied changes:


using requests third-party library with a shared session
Python 2 and 3 compatible
using class for sharing "session" and a set of visited urls
separate methods to visit urls and download images
if __name__ == "__main__": is used to avoid the code being executed on import
changed the way image filename is determined (probably still not the best way)
handling relative urls as well as absolute