Always room for improvement. A glaring issue as far as I'm concerned:
What's the point of the "rats/bats/ghosts/goblins" inserts on the left ramp, and the "play the organ/living dead/grave digger/chainsaw mode" on the right ramp? They light up in turn, but don't seem to have much of a purpose otherwise... Am I missing something? You cycle through them, and get points of course, and perhaps trigger a "points/hurry-up mode" but they don't really serve any unique/interesting purpose otherwise; I expect there was some planned use for them and it just never made it into the code.
I think there's room to improve on multi-ball as well. Start it, shoot left ramp, shoot right, spell "crypt" again - maybe add something for spelling "keeper" while multi-ball is active?
I know there are limits in adding new content (unless you find a bunch of unused audio call-outs, unused animations, and snippets of code that are otherwise bypassed that provide a starting point), but tweaking the above I think would be useful.