Credit to pastebin for some code snippets.

Hope this saves someone some time and effort.

#!/usr/bin/python
'''vcard.py - Update your XMPP vcard photo with the image you provide

Usage: vcard.py image_file jid password
'''

from xmpp import JID, Client, Iq, Presence, NS_VERSION, NS_VCARD
import sys
import os
import time
from base64 import encode, decode
from hashlib import sha1

try:
    file=os.path.expanduser(sys.argv[1])
    jid=sys.argv[2]
    password=sys.argv[3]
    resource='vcard'
except:
    print >>sys.stderr, __doc__
    sys.exit(2)

NS_VCARD_UPDATE = 'vcard-temp:x:update'
NS_NICK = 'http://jabber.org/protocol/nick'

def hash_img(img):
    return sha1(img).hexdigest()

def base64_img(img):
    return img.encode('base64')

def get_img(file):
    try:
        os.stat(file)[6]
        fh = open(file, 'rb')
        img = fh.read()
        return img
    except Exception, e:
        print >>sys.stderr, e
        sys.exit(2)

def get_mime_type(file):
    try:
        ext = file[-4:]
        if ext == '.png':
            mime_type = 'image/png'
        elif ext == '.gif':
            mime_type = 'image/gif'
        elif ext == '.jpg' or ext == '.jpeg':
            mime_type = 'image/jpeg'
        else:
            raise ValueError, "Wrong mime-type detected. Check file suffix."
    except ValueError, e:
        print >>sys.stderr, e
        sys.exit(2)
    return mime_type

def send_vcard(conn, base64_img, mime_type, nick):
    iq_vcard = Iq(typ='set')
    vcard = iq_vcard.addChild(name='vCard', namespace=NS_VCARD)
    vcard.addChild(name='NICKNAME', payload=[nick])
    photo = vcard.addChild(name='PHOTO')
    photo.setTagData(tag='TYPE', val=mime_type)
    photo.setTagData(tag='BINVAL', val=base64_img)
    conn.send(iq_vcard)

def send_presence(conn, status, hash1, nick):
    presence = Presence(status = status, show = 'xa', priority = '-1')
    presence.setTag(name='x',namespace=NS_VCARD_UPDATE).setTag(name='photo',namespace=NS_VCARD_UPDATE).setData(hash1)
    presence.setTag(name='nick',namespace=NS_NICK).setData(nick)
    conn.send(presence)

if __name__ == '__main__':
    img = get_img(file)
    j=JID(jid)
    cl=Client(j.getDomain(),debug=[])
    conn=cl.connect()
    if not conn:
        raise Exception, 'failed to start connection'
    auth=cl.auth(j.getNode(),password,resource,sasl=1)
    if not auth:
        raise Exception, 'could not authenticate'
    send_vcard(cl, base64_img(img), get_mime_type(file), j.getNode())
    send_presence(cl, 'Updated vCard Image', hash_img(img), j.getNode())
    time.sleep(1)
    cl.disconnect()