This is a small CLI-tool that you can use to read your WBPattern.prefs 
from CLI and use its output in scripts.

v1.0
~~~
* First release.

Usage:
~~~~~
The arguments:

0 - Will output Workbench picture fullpath. Will return a WARN if it's a
    Pattern and not a Picture.
1 - Will output Windows picture fullpath. Will return a WARN if it's a
    Pattern and not a Picture.
2 - Will output Screen picture fullpath. Will return a WARN if it's a
    Pattern and not a Picture.

Full ASM Source code is provided in archive with some examples.

Written with Devpac 3.18 on a Vampire :-) !obv

PERMISSION  UID  GID    PACKED    SIZE  RATIO METHOD CRC     STAMP     NAME
---------- ----------- ------- ------- ------ ---------- ------------ ----------
[unknown]                  579     856  67.6% -lh5- 9da7 Mar 19 19:26 GetWBPattern
[unknown]                 1786    6976  25.6% -lh5- 5ea8 Mar 19 19:26 GetWBPattern.asm
[unknown]                35276   35276 100.0% -lh0- 17f8 Mar 19 19:30 GetWBPattern.jpg
[unknown]                  404     817  49.4% -lh5- 47fe Mar 19 19:35 GetWBPatterns.readme
[unknown]                  119     234  50.9% -lh5- 94c1 Mar 19 19:26 GetWBPatterns.run
---------- ----------- ------- ------- ------ ---------- ------------ ----------
 Total         5 files   38164   44159  86.4%            Mar 19 18:32