xfburn -i <image>
Xfburn comes from Salix. Salix 14.0 is based on Slackware 14.0, it uses a.o. the gtk+2 libraries from Slackware.
The above command with gtk+2-2.24.10 from Slackware 14.0 is ok.
The above command with gtk+2-2.24.17 from Slackware Current ignores the <image> argument.
The above command with gtk+2-2.24.18 (just built by me) is ok again.
Please update Current's gtk+2 to 2.24.18.