The image shown below is of a three dimensional Diffusion Limited Aggregate. A simple three colour parallel lighting model is used to highlight the faces. More information on these models at: DLA.
The images shown below are of a smallish diffusion limited cluster-cluster aggregation simulation. The left (or top depending upon the aspect ratio of your browser window) is at timestep 243, the other at step 486 of a simulation with a downwards drift field. The second image has exactly 100 clusters or aggregates. The red cluster in both images is the largest one. The simulation makes a fascinating movie - unfortunately too large a file to show here.
This image shows a snapshot of a two-dimensional molecular dynamics simiulation. In this system eight species of particles interact in a box with reflecting walls. Particles attract other particles of the same colour. The solid and dotted lines show a proximity graph - edges indicate a strong interaction. The surrounding circles indicate particles' preferential particle-particle distance - the separations they would adjust to in a low temperature crystal.
Also my PhD Thesis from Edinburgh University, 1991, contains ideas and a discussion of Growth in Domain Alloys. The [PDF] document is a compressed and reformatted version in LaTeX report style. The original was somewhat novel being one of the earliest all-electronic theses at Edinburgh. The then thesis style required double spacing and single sided. This current version is re-formatted for a more modern era.
There are a number of models that exhibit growth and which can be used to compare and hence chracterise/classify an arbitrary real-world growth system. Another simulation model that generates interesting pictures is the self-avoiding-walk model.