It appears that someone has been posting pictures of an unreleased Sony Ericsson phone from another unreleased phone. To clarify, both the phone taking the picture, and the phone in the picture are unknown.
The phone taking the pictures have been uploaded to Picasa from a Sony Ericsson phone with model number LT15i. That phone is rumored to be the Sony Ericsson Anzu, also going by the name of Xperia Arc, Xperia Duo, and Xperia Neo. This could be the next version of the X10 series. The pictures of this phone do not appear to be at a full 12 MP, so it could be shooting at lower resolution or we could be looking at a completely different phone.
As for the phone in the picture, the design reminds us of the Sony Ericsson Vivaz from the curved top, with the exception of the microUSB and headphone jack on the side, instead. The picture shows what could be Android 2.3 (Gingerbread) and a front-facing camera. This phone is rumored to be codenamed Hallon with model number MT15i. Another phone that has been given a model number is the PlayStation phone–R800a in the U.S. and R800i, internationally. Sony Ericsson has mentioned that several phones will be announced at February's Mobile World Congress, and I think we know of at least three.