Hi, PE -
I have been following your story. What you're going through is brutal, and I'm glad you have people to share it with, who can identify with some of what you're experiencing...
There's some really good advice in this thread. I was really struck by what Scratchme said...
'It will get real for her when she realizes that you are no longer trying.'
I found this to be the case in my own life situation. The 'shunning' thing became a contest of endurance and will.
And even if you win, the 'victories' seem pyrrhic in nature, when considering what the costs are in terms of time and suffering.
Keep the lines of communication w/ your brother. As has been mentioned, his willingness to break the rules and speak to you is promising.
If you abide your mothers wishes and stop sending her pictures, she will miss receiving them. Whether-or-not she admits it to herself or any else is immaterial.
The only way I found to turn this crap into something positive, is that it steeled my resolve to provide my children with a WT-Free childhood. This poison ends here.
There is a case to be made that what is really best for your daughter, is total separation (or at least as long as WT 'rules' are applied in all their rigidity). Your mom is seeking a comfortable detante of sorts: where she gets to apply the shunning rule but still have access to her granddaughter. You must, at all costs, deny her any comfort - IMO.
Good luck with whatever you decide. Keep us posted.