To change the amule look in rh9 you have to change your ~/.gtkrc
The rh9 defaults are set up to give your system the rh Bluecurve (tm) look

Just look into /usr/share/themes and check what gtk (1!) themes you can find.
This is a rh standard ~/.gtkrc:
# -- THEME AUTO-WRITTEN DO NOT EDIT
include "/usr/share/themes/Bluecurve/gtk/gtkrc"
# -- THEME AUTO-WRITTEN DO NOT EDIT
Change it to (this should work on almost every rh9 box)
include "/usr/share/themes/ThinIce/gtk/gtkrc
and restart amule - you should see a difference. Now you just have to find a theme you like.
There sure is a better way to change the themes - take a look into your Preferences Menu or the gnome-control-center to figure out how.