Pat, I did this pdf explaining about selections to get good results. I hope it can be useful.

A warning.
Maybe you can this message
"ERROR! Folder for patterns does not contain any valid pattern. Exit."

When you get this error, the "filter for patterns" you entered is not a substring included in any active pattern set.

Sometimes the problem is difficult to detect, because Gimp takes care also of the "blank spaces" which the human eye does not "see"

For instance, if you enter as substring "200 "(*), you get the error, while if you enter "200"(*) it works, because in the first case Gimp looks for a pattern containing the substring 200 followed by a blank space, and there is none because all my small patterns have a Q immediately after 200.

(*)ignore the "", they are there for clarity of this post

thanks Issabella for your tut

Outstanding images Issabella! Very creative.

Thank you Dinasset and Racer-X,

I did these outcomes with different selections.

Thank you, Issabella. Your images are exceptional.

Thanks Pat.

I applied "DN_ NuancedLevels" and then I applied "DN_Print on Stones"
To get a perfect tiled shape (without splitting tiles in the result) my selection was 1000*600.

, enjoying this filter so much.

I experimented with putting paths on each vertical and horizontal tile line, and creating a bump layer. This gave the tiles a bit of depth.

Pat, nice results with this filter.
PhotoMaster, I really like your outcome a lot. Good experimentation, too.

Thanks, Issabella. PhotoMaster, I like your idea. I'll try it.