Russian website wp7forum.ru appear to have shots and information about the upcoming Windows Phone Tango release. They highlight a number of changes, including the support of additional countries, an increase on the amount of preloaded apps (from 16 to 40), SIM contact management and importing (ideal for new owners) and finally the ability to add multiple attachments to MMS messages.
There’s also details of a potential issue with devices having 256MB. This is a little puzzling, as Microsoft have also poked fun at Android “fragmentation”. If these details are correct, it’s instant fragmentation for Windows Phone. Devices with 256MB running Tango will be unable to install certain apps and there’ll be other restrictions including podcasts not being manageable, lower-quality video streams and Tiles not updating properly.