If you're using iTunes on a PC, then you should definitely check out SyncMyPortable. It was written to allow you to sync all of your iTunes music (and videos) with any portable audio device that supports Mass Storage (such as the SE phones). It has options to automatically include the album artwork for you (including the new downloadable album artwork in iTunes v7) as either a free-standing JPG image file in the album folder, or embedded within each of the song files themselves. It has many other advanced options such as auto playlist generation, on-the-fly music format conversion, etc., etc. I use it all the time with my W950i. You can read more about it here:
BTW, the W950i can display album artwork images of any size. It simply resizes them to fit the screen as needed.
Also, I believe that you can see lots of screen shots of the W950's user interface (including the Walkman player with album artwork) in this excellent review:
