Twitterers on smartphones can already upload pictures using email or a Twitter client such as Gravity but the use of MMS makes it much more convenient for the majority of users, and assuming you have an MMS bundle, it should cost less (although if you have a data bundle with no MMS, stick with the upload route!).
That might not be the end of it though, as Steve O'Hear writes at TechCrunch Europe:
However, SMS and MMS integration is just the start, say Orange. The telco, which operates as a quad-play in some countries (IPTV, fixed line, mobile and broadband), plans to work with Twitter to “create a range of simple but innovative new services” right across its offerings. One idea is to put Twitter on the television through ‘interactive’ Twitter feeds that appear alongside particular TV programs. For those of us who regular follower Twitter during shows like the UK’s X-Factor, this may make some sense.
(Also congrats to Steve O'Hear on the new editor role at TC:EU)!