If you want images of any sort, I'd say Netscape 3 on an SE/30, though there will be no support for modern standards such as CSS. On my old hardware I personally really like WannaBe, which is text-only but lightning fast. If the accessibility standards were universally applied (every site is supposed to have a workable text-only version for the visually impaired), WannaBe would actually be a viable browser for most old machines.

Cyberdog is also fun to see in action on something like a Quadra, but I don't think I would want to run it on an SE/30.