Is there a node for distributing shapes from densely packed to spaced out.

Hi,
Tile sampler will do that. 

To replicate your example I :

1. Plugged a shape in the pattern input.

2. Plugged a linear gradient via a curve into the displacement map input

3 Inside tile sampler I set : 
3.a. Tiling mode to absolute then no tiling

3.b. X amount to 16 and y amount to 12

3.c. Selected pattern input
3.d. Size mode to 'Keep Ratio' 

3.e. Displacement Map intensity to 1

3.f.  Displacement angle to 180 degrees

4. Then I adjusted the curve node to get a suitable distribution. You could use a levels node instead of the curve but the curve gives more control.

Dave