blobwars installs a .desktop entry, but not an icon to /usr/share/pixmaps, which is where some desktop environments (at least xfce4) check for icons. Reproducible: Always Steps to Reproduce:
Created attachment 54176 [details, diff] patch to ebuild to install an icon
The current ebuild installs three icons: /usr/share/icons/mini/blobwars.png /usr/share/icons/large/blobwars.png /usr/share/icons/blobwars.png
I did see that, but I had thought that /usr/share/pixmaps was where icons should be (doicon installs there). Aside from that, it would seem to be more an xfce bug not having /usr/share/icons in its icon search path.
yep, the freedesktop standard says things snould look in /usr/share/icons before /usr/share/pixmaps. Both gnome and kde work correctly in this regard. I recommend you get xfce to follow the standard.
A filed a bug to xfce about this over at http://bugzilla.xfce.org/show_bug.cgi?id=861 regarding this. So, it would seem that an icon would have to be installed in the /usr/share/icons/hicolor/ structure, in addition to the icon being square (right now its rectangular). I've sent an email to the blobwars author, so hopefully this can be fixed upstream.