I don't think empeg guys will spend much time on this, but we can already do that ourselves. There is a program somewhere around that replaces Tux logo, right? Now, just store logo files in a known directory under the name same as the name of the artist, and write a small program (even shell script) that runs in the background, reads /proc/empeg_notify (of course, with HiJack installed and notify switched on), detects change of artist and replaces logo as needed.

Feel like trying your hand at it? I believe somebody on the board provides accounts on his server for cross-compiling.