When you say your last B/T update, what update do you mean. Is it the BT Homehub update, BT Netprotect update or BT Helpdesk update or some other update?
In order to help we need to know which update you are refering to.
I take it you mean from when your BTYahoo webmail upgraded to the new webmail?
Are you using webmail or an email client such as Outlook or Windows Live Mai?
What happens when you try to attach a photo?
Can you attach documents or is there a general problem with all attachments?
There have been other reports of problems with attachments to BTYahoo mail.
The first thing I would try is a factory reset of your Homehub by pressing a pin into the red recess button on the rear for about 20 secs. Once this has been done and the hub restarts try attaching a photo.
If this doesn't work then report back and we can try some of the other fixes.