Hi,
Is there an image viewer for Ubuntu/Lubuntu that will view Amiga iff images?
ImageMagick does that, and it's both more lightweight and part of the distribution (i.e. automatic updates). IM is a collection of console tools, mostly for image converting, resizing etc. One of the tools is called "display", that one handles ILBM.
Install ImageMagick, right click an ILBM picture, select "Open with..." (or whatever it's called on Lubuntu) and select "ImageMagick (display)" from the list. You can also save that choice as the default tool.