If you don't mind, here's my current understanding of how your image generation works - how close am I to correct?
So each card has a number of objects associated with it, such as "sea", "sun", "star", "figure", "mountains", "city" etc. These objects work in different ways but generally have an actual position on the card, and often an associated "mask" that determines the shape of their "density". Objects also have a flow field, which I take it is like a vector field, which influences the direction lines will take, if the line is associated with the object. Each object also has a set of parameters which determine how lines will be drawn; this can make lines strictly follow the flow field, or wobble around, or travel at right angles to the flow field, or zigzag, etc. etc. It can also make lines thicker or thinner, and can apply certain colors to the cells which are produced by the lines.
Drawing takes place via a number of growth points traveling around on the card. Each of these growth points belongs to one of the "objects" (as I've been calling them), but they're all on the same card so they can collide with lines being drawn by other "objects". One thing I'm not clear on, is how many growth points initially are placed onto the card. Do separate objects maintain separate pools of points, or are they all thrown in together? But anyway, just like with the famous "Substrate", when a growth point collides with an existing line, it gets moved someplace else on the card.
As I understand it, growth points actually spread outward in two directions (unlike Substrate). So I think maybe both sides of the line need to "land" on an existing line before the line "dies" and a new growth point gets placed. When both sides of a line have "landed", typically it would form a closed shape which I think gets called a "cell". I'm guessing that the growth point which completes a "cell" influences what color it eventually gets colored, via the parent object that owns the growth point.
New growth points get placed randomly on the card, according to the "density" field. Looks like when a new growth point is placed, it drains away some of the density nearby, so that growth points are unlikely to begin too close to where one has already been. There's also a limited number of total growth points, so that eventually they run out and the card is finished.
I think that covers most of what I understood. Is that about right?