Monkey Messenger is a kind of new client for linux, it's done in C# and has a very clean and cool interface based on the idea of the official client.
It has support for Personal Messages, and Display Pictures, but on my test it could not send Pictures to Microsoft official client. Sadly, the developer got kind of sick of dealing with msn protocol (witch seems to be insanely confuse) as he said on its blog
and the svn activity stopped. Hope it can continue developing it, it looks very promising.
Galaxium is another Msn client done in C#, The project was started in 2004 and is now on the 0.6.0 version. It feature a very well done interface but as the msnp2p is not implemented, display pictures, file transfers, and custom emoticons seems not to be implemented.
Sadly, looking at the svn the last change to the code was about 3 months ago too, and i could not find any forum or way to reach the developers. So everything we can do is wait and pray that the project is not dead.