Google has expanded carrier support for picture messaging over Google Voice. After working with carriers for support, users on 100 different North American carriers — including AT&T, Sprint, T-Mobile, Bell Canada, Rogers, Telus, and many more — should now be able to recieve MMS messages on their Google Voice number. There's no word on any carriers outside of North America mentioned. Also, Verizon is conspicuously absent from the list, and users report that MMS over Google Voice isn't working on Big Red.
It's worth noting that there was limited support for picture messaging on some carriers at some times since the Hangouts integration, and we've been able to verify that it's working right now on AT&T, Sprint and T-Mobile as expected — with a few glitches here and there.
If not being able to receive picture messages was holding you back from using Google Voice, you might want to take a look now if your carrier is supported.
Source: +Alex Wiesen