There are various patterns. This a brief summary you can have a look
QRD Diffuser Well Depth Calculator
According with Trevor J. Cox and Peter D'Antonio page 236 chapter 9.3 from the book ''Acoustic Absorbers and Diffusers'' (by the way very good book if you want to buy it) the theoretical approach differs from the reality. So i chose 10 cm well widhts instead of 5cm in order to go at low frequencies. The period was choosen to be 7 since i wanted to have more repeatability (4 diffusers total at each side) than going with a large period and just making maximum 2 diffusers each side.
If i can be excused from the authors i copy this phrase:
''For the diffuser to behave optimally, the device must be periodic....
...It must be remembered, however, that manufacturing costs are likely to mean that a narrow base shape with a large number of repeats is going to be the cheapest build''
I think you cannot base the models only in theory but in practise, and the book provides evidence from expreriments they did, so it is a respectful source.
The ceiling diffusers (skyline) is the basic shape that is again verified in the book. I believe in the idea to create diffusers that work at different frequencies for more variability. Eventually at our webpage we will create different sections with gathered photos of how the job was done (step by step), we are just to bussy at the moment ordering equipment. It is not difficult to make them if you have the plans and the materials, it is jsut time consuming, but you save money in labor by doing it at your free time
Nikolas