From Fedora Project Wiki

Just a head's up that this tutorial can't be done on Fedora 15 as for some readon the GIMP is not compiled with xpm support (???). On F15 I used a combination of the GIMP and xpaint to make it work. This does work under F14 despite the fact that both Fedora versions are current with 2.6.11 version of the GIMP.

Bug has been submitted here:

Bryan -