The 'Photos' tab feature does still exist, however, it's not visible while the phone indexes them all.
If you don't have any 'Photos' tab, give it some time. I found it took about 48hrs for it to become visible again, though the amount of message photos you have may extend/reduce this time.
If you do have the tab, but it's incomplete (not all pictures shown), open Settings and go to Search > Messages. Turn off both toggles, wait a few seconds, and toggle them back on. The tab will likely be gone again but should reappear within 48hrs, this time displaying all the pictures.