There is software to do that; needs to be run on the empeg commandline though.
If I've understood it correctly, it's a binary player hack - the software scans the player binary for where the Tux Much image resides and then replaces those bytes. I don't think anythings changed so that it can't be used.
It's called setvisual and downloadable from
Frank van Gestel
I think the README is out of date, but IIRC, if you run the program w/o arguments you'll get a help text.
Edit: If I'm unclear above: it'll replace the image used in the static visual (Tux)
/Michael