The storm cards were cool. they're basically JPEG compressors/decompressors that were much faster than any 68K processor. You need the control panel so it will speed up any operation that calls on the routines it can handle.
It's most current use would be to speed up web browsing on a 68K Mac, like a non-AV Quadra.
BTW, the Storm control panel can also be used to speed up Web Browsing on an AV Quadra WITHOUT the Storm Card (It uses the DSPs).