I was going to call this "Pimp Your Pin", but decided on a more descriptive title.
A week or so ago, I spent a few hours installing some mods to my Twilight Zone.
The first one was the backboard decal. Easy to install, though the decal needed to be trimmed a bit to fit. A nice improvement to the look of the machine.
The next one was the door flasher kit. This replaces a feature that was cut to reduce the cost of the machine. An easy enough install, but frankly, it really doesn't make much of a difference.
Next was the gumballs, a set of 60 small plastic gumballs that fill in the outer clear part of the gumball machine. You can either take the gumball machine apart (a lot of work), or you can do it more simply, and squeeze them in the space between the between the outer shell and the inner section. To do this, you have to press them in really hard (ie so hard your thumbs hurt), but it's worth the effort. This is definitely a nice upgrade.
I also added a Gumball flasher from PinGizmos. This adds few white LEDs to light up the gumball machine when the load light is flashing. The mod requires a small mod to the plastic divider, easily accomplished with a diamond wheel in the Dremel. This is a good mod, and really adds something to the machine.
The biggest upgrade was a set of new speakers. If you've ever pulled factory speakers out of a car, you've already seen the quality of the stock speakers in the pinball. Williams pins actually have 3-way speaker systems, with a separate woofer, midrange, and tweeter. This set has a bigger woofer and upgraded mid and tweeter, and the sound difference is pretty impressive. Much better on the music, and the deep bass sounds actually make the pin vibrate.