I wrote my own Life game in Visual Basic 6, and experimented with rules (first starting with the official GoL rules to make sure the program itself was working correctly). I found there's this one rule, that if you start with a decent sized square region of the particles placed randomly in this square region, it first morphs into diamond shape, and then remains VERY stable. On average, it seems to neither expand nor contract, at least not during the several minute long period that I was watching it. The rule is:
Birth 3,4,6,7
Stay 3,6,7,8

I don't know if this is an already named rule of not, but if not, I think it should be called "VG555 Life" (based on an abbreviated version of my username). This should be added to TPT's list of Life particle rules, and be given the shorter name VG5L in TPT, due to the 4-character limit for particle names in TPT.

So yes, please add this to TPT.

LBPHacker:

I may add this later, there's no reason not to. One thing for certain is that if it does make it into the game, it'll be called something with a more... objective ring to it. Something like "STBL". I should add though that I have tested the rule and it didn't seem too stable to me.

I tested it in the following conditions.
Playing field is 512x512
Initial condition is randomly placed life particles in a 256x256 square region who's center is located at the center of the playing field.
Wrap around occurs at the edge of the playing field.
Each life particle only has 2 states, alive and dead.
The birth and stay rules are B=3,4,6,7 and S=3,6,7,8
The region to consider for the birth and death rules is the 8 cells surrounding a given cell, thus the cell itself is not counted for the birth and death rules.

Because they are randomly placed in the square in the center as the initial condition in my test. Some configurations tend to be stable, but every once in a while it crosses the border and connects to itself from the other side. When this happens, the blob of life cells tends to grow (not remain stable). But if there is no connecting back to itself, it tends to be stable. Starting with too small of a region of initial seeding might (in some conditions) cause it to collapse to nothing. But in general, when tested under the conditions I stated in my first paragraph, the blob of life particles tends to be stable (neither having an overall growth or shrink). Any slight alteration to the birth and stay rules will destablize it.

When I tested it by running it at maximum CPU speed (which is more generations per second than there are frames per second on the monitor, so only once every several generations could be shown) I discovered that letting it run for like 10 minutes would usually not result in significant change in overall size. On average, for every expansion of the edge of the blob of life cells, there was a shrinkage somewhere else on the edge of the blob.