Sometimes things can’t be drawn as a cell but also don’t work well as a token.
Things like stairs for example. There’s almost a standard in D&D map drawing to use a triangle made of lines to denote stairs, seen in this map or this map-drawing legend.
There’s also other things like traps, rubble piles, or trees that don’t quite work well as tokens since they don’t need to move and are often drawn below the player tokens as a detail of the terrain. It’d also be nice to denote cliff ledges (see bottom left of the above legend), which can’t be clearly shown using just cell colors or edges. It’d also be nice to have symbols for things like +30ft to show that the elevation changes like in this map.
I know it might be considered to be adding complexity, but it’s something easily done on a whiteboard that doesn’t really have even a work-around in Shmeppy.