Hi all! Came a bit late to the party this time, but I managed to spend some odd hours over the last week coming up with a nice tilable pattern - here's my reference, and what I've done so far:

This is the OpenGL render:

and lastly an Iray render:

Not sure what's causing those weird jagged edges, I'll have to experiment with it a bit more. As for further work I'm thinking about adding a surround over the main tiling pattern to make it look closer to the ref image - so this pattern will be in the center, then around it would be a white surround kinda like a shoe tread, then maybe a green weave for the outer section. So hopefully it will look almost like someone took a sports shoe and just flattened it out.
Haven't created any parameters so far but will most likely go for some fairly basic stuff; colour, tile size, tile rotation and simple roughness controls.
Anyways, any thoughts or improvements (especially regarding those jaggies on the iray render) would be appreciated! Ty