It's been a long time coming, but Google Voice has now added MMS support from almost every major US carrier. Except for Verizon, that is. Your Google Voice number should now be able to receive in-line MMS photos from people on AT&T, Sprint, T-Mobile, or another of "nearly 100 different North American carriers." (In Canada, Bell Canada, Rogers, Telus, and others are playing nice with MMS / Google Voice compatibility.) "For too long, however, Google Voice users would miss these messages for lack of MMS support," wrote Googler Alex Wiesen. Thankfully that's no longer the case for most carriers, but apparently Verizon still isn't on board. The largest US carrier isn't mentioned by name as a participating partner, and Wiesen takes a not-too-subtle poke at Verizon by adding "If you’re a carrier, and you want to enable MMS support for Google Voice, please let us know. We’re big fans of text messaging interoperability."
So photos should now be appearing in-line, but outbound messages are another matter. Some users who've already merged their Google Voice and Hangouts accounts are reporting success when sending out pictures from a Google Voice number. But results are mixed; others are still seeing a shortened Google link that points to an uploaded version of their photo on Google's servers. Perhaps that's to be expected, since it may take some time for Google and carriers to work out all the kinks. Hopefully Verizon will come around and add its own support before long, but that's probably a tad optimistic.