Sorry about bumping an old thread, I came across it while looking for some LEDs to outfit one of my games.

In any event with regards to dimming - LED lamps require a pulse width modulation circuit to "dim" and even then it is limited. A LED requires a min voltage to "turn on" (electrons start to flow) and remains on until the voltage drops below this threshold, increasing this voltage past the "turn on" voltage does not make it brighter. Unfortunately it is not a as simple process as incandescent bulbs which dim as voltage drops. So, no adding resistors/caps will not help.

BTW - awesome the way the Fish Tales playfield is lit in the posted pictures, an improvement for sure.