Well, are the rock monsters and other creatures going to be in the game? Presumably they'd be controlled through AI? Could you make it so that maps are generated as a grid of interchangeable tiles? This would make creating the maps significantly easier and perhaps even open up the possibility for an end-user level editor.
Also, I wouldn't mind if the wall textures/geometry were remade. Perhaps a mesh which has some of the features of the rock face protruding from it? Maybe you could have a small selection of slightly different tiles for each wall "type" so the caverns aren't so monotonous.
There are so many ways in which the concepts and graphics from the original game can be improved upon. Truly an exciting opportunity.