TIFF is Tagged Image File Format. It's not an compression format, though it supports many compressions. With monochrome data, the G4 fax encoding is truly spectacular.
You could probably implement GIF with a vestigial compression that merely looks like LZW. You wouldn't get any compression, but a reader would still find that it's a complying format.
SVG wasn't available in IE prior to version 8. Other older browsers that didn't do SVG have almost all been upgraded, so its reasonable to require that.
If you want to use SVG, but fall back to VML back as far as IE5, I recommend the Raphael Javascript library at . It does what it says on the box. But these days I'm just using SVG.
Clifford Heath