A Mac Classic? You could've said so in the first place. Jade won't help you there, AFAIK.

You only mentioned gifs and bitmaps specifically, but if you also wish to view jpegs, be aware that viewing them on a monochrome compact can sometimes provoke "out of memory" errors. In those cases, convert to gif first, then display. For this purpose, get jpeg convert, then view the result with gifconverter (or gifwatcher). I used to use those apps on my Plus, and I remember thinking that gifconverter did a fine job of halftoning for display on a non-greyscale monochrome mac.