Thanks for the positives, Will darken my background some...

Eventually I just want to produce a crosshatch effect that fades to black around the walls. I'll see how easy it is to get that effect!?

At present my DPI is all over the place... I'm aiming high knowing that I can always drop down later. High DPI allows me to keep the quality up.

I think I'll take a stab at the dark outer pattern and maybe work on my slabs adding a more uneven rock texture next.

Cheers everyone for the tips and feedback.