auto tb
iface tb inet6 manual
        pre-up  setsid /root/tb_userspace tb IPV4_ENDPOINT > /dev/null &
        up      ifconfig tb up
        post-up ifconfig tb inet6 add IPV6_ADDRESS/64
        post-up ifconfig tb mtu 1480
        post-up ip -6 route add ::/0 dev tb
        down    ifconfig tb down
        post-down       route -A inet6 del ::/0 dev tb
        post-down       killall tb_userspace

Original source

#!/usr/bin/python
# -*- coding: UTF-8 -*-

from mutagen.flac import FLAC
from mutagen.mp3 import MP3
from mutagen.id3 import ID3, APIC, error
from mutagen.easyid3 import EasyID3
import urllib2,urllib, os, sys
from xml.dom import minidom
mainenc = sys.getdefaultencoding()

def getImage(artist,track):
	try:
		req = urllib2.Request(url='http://ws.audioscrobbler.com/2.0/?',
			     data=urllib.urlencode({
				'method':'track.getinfo',
				'api_key':'b25b959554ed76058ac220b7b2e0a026',
				'artist':(artist).encode('utf-8'),
				'track':(track).encode('utf-8'),
				'autocorrect':1
				}))
		f = urllib2.urlopen(req)
		xml = f.read()
	except:
		print "Failed @ %s - %s" % (artist.encode(mainenc,'ignore'),track.encode(mainenc,'ignore'))
		return None
	nodes = minidom.parseString(xml).childNodes
	try:
		url = nodes[0].getElementsByTagName('image')[-1].childNodes[0].toxml()
	except Exception, e:
		print "Nothing found for %s" % track.encode(mainenc,'ignore')
		return None
	req = urllib2.Request(url=url)
	u = urllib2.urlopen(req)
	return u

folder = unicode(raw_input("Podaj swoj folder muzyki (np. D:\muzyka):\n"))

for root, dirs, files in os.walk(folder):
	print root.encode(mainenc,'ignore')
	for i in files:
		if 'folder.jpg' in files or 'Folder.jpg' in files:
			if os.path.getsize(root+"\\"+'folder.jpg') > 0:
				break
		ext = i.split('.')[-1].lower()
		if ext in ['flac','mp3']:
			try:
				if ext == 'flac':
					audio = FLAC(root+"\\"+i)
				elif ext == 'mp3':
					audio = MP3(root+"\\"+i,ID3=EasyID3)
			except Exception, e:
				print e
				continue
			if audio:
				img = getImage(audio['artist'][0],audio['title'][0])
				if img is not None:
					print "Writing to %s" % root.encode(mainenc,'ignore')
					f= open(root+'\\folder.jpg','wb')
					f.write(img.read())
					f.close()
					break

print "Done"

+ bonus, executable version

from mutagen.flac import FLAC
from mutagen.mp3 import MP3
from mutagen.id3 import ID3, APIC, error
from mutagen.easyid3 import EasyID3
import urllib2,urllib, os
from xml.dom import minidom

def getImage(artist,track):
	req = urllib2.Request(url='http://ws.audioscrobbler.com/2.0/?',
			     data=urllib.urlencode({
				'method':'track.getinfo',
				'api_key':'b25b959554ed76058ac220b7b2e0a026',
				'artist':audio["artist"][0],
				'track':audio["title"][0]
				}))
	f = urllib2.urlopen(req)
	xml = f.read()
	try:
		nodes = minidom.parseString(xml).childNodes
		url = nodes[0].getElementsByTagName('image')[-1].childNodes[0].toxml()
		req = urllib2.Request(url=url)
		u = urllib2.urlopen(req)
		return u
	except:
		return None

for root, dirs, files in os.walk('D:\\muzyka'):
	print root
	for i in files:
		if 'folder.jpg' in files or 'Folder.jpg' in files:
			if os.path.getsize(root+"\\"+'folder.jpg') > 0:
				break
		ext = i.split('.')[-1].lower()
		if ext in ['flac','mp3']:
			try:
				if ext == 'flac':
					audio = FLAC(root+"\\"+i)
				elif ext == 'mp3':
					audio = MP3(root+"\\"+i,ID3=EasyID3)
			except:
				continue
			if audio:
				img = getImage(audio['artist'][0],audio['title'][0])
				if img is not None:
					print "Writing to %s" % root
					f= open(root+'\\folder.jpg','wb')
					f.write(getImage(audio['artist'][0],audio['title'][0]).read())
					f.close()
					break

print "Done"

Albumarts are downloaded from last.fm