Console / terminal File viewer
One of the nice things about forums, IRC etc, is you get to find out about all sorts of software that is really useful. Sometimes this just seems to address fit what you want.
One such example is a program called view
manpage description is:-
mcview – Internal file viewer of GNU Midnight Commander.
You can use view to view pdf files, or rather the text content within, which is pretty good, very useful if compiling $\LaTeX$ with pdflatexfor example.
You can also use view on a png graphics file, however this just displays information about the file, for example resolution. Again useful from the terminal / console at least.