Alright,
Here are my findings. As I mentionned in my previous post, i have installous, notifier+, sbsettings and anyring installed from cydia. I have fixed my issue on 2 different phones by doing the exact same procedure. I have confirmed it resolves the imessage picture issue and the Facetime connection freeze. (Also reported as a oneway freeze)
1. Went in cydia.
2. Uninstalled Anyring
3. Shut imessage and turned of mms from "Settings, messages"
4. Rebooted
5. Turned on the imessage and mms (waited for activation).
6. Imessage can now send pics and facetime works again
For those of you who do not have anyring, check if you installed any app to constumize your ringtone (for calls or messages). As you may have noticed, facetime uses a different ringtone than the default ring you can customize with 3rd party apps. I suspect that when you use anyring or another app that would allow you to change your ringtone, and that you place a facetime call which invokes a default ring, things go wrong...
I know its vague and just a theory but my issue is 100% resolved. The issue is deffinitly caused by something that you installed with your jailbreak. If the jailbreak itself had this effect, we would most likely see it all over the place. But we are only a handfull of people with the issue.
Start by removing cydia apps that have to do with rings, messages, calls in general. Shut imessage and reboot and restart imessage. I am sure you will identify the offending app as i am sure there could be more than one.
Please let me know if this info helped resolve the issue.
Cheers