Okay so I haven't played since 3.4 or 3.7 or thereabouts. I forget. But the last time I did, disabling shaders reverted the game to its original old low-poly, sort of cel-shaded looking graphics engine. It was certainly a boon for performance.

Now I'm looking into what games I can cram onto my netbook, grab the latest Toribash, and find that even with shaders disabled it looks considerably more high-end than it used to. Doesn't run all that great either. Is there some way to force the old appearance via a command line or something?

You can still use an older version of Toribash if you prefer. As far as disabling the high-end graphics and such I am not sure. For now you are best to just stick with an earlier version.