Found where this gets handled and there is room for up to three more statuses.
The function starting at 0x5BA1EB translates the actor's status with a shader index. The shader has an "activator" of either on or off (I'd call it an alpha channel, but there is handling for a third value that I'm not sure what it would do) and an RGB color value to it. There are 12 of these four-byte shaders starting at 0x8FE150 and it looks like only these are used:
Poison: 1
Berserk: 3
Petrify: 5
Peerless: 6
Manipulate: 7
Darkness: 8
Regen: 9
Slow-Numb: 10
The activator mentioned is also what prioritizes which shader gets used in the event of multiple shading statuses. It can be optimized a little to perhaps include a new status/shader combo.