Lots of configuration can done for thumbnails if they are generated by the cadworker. The cadworker uses pvsthumb.exe to create the thumbnails from the just created pvz file (like Tom just mentioned).
Take a look at CS46170: https://support.ptc.com/appserver/cs/view/solution.jsp?n=CS46170
This issue actually deals with complex models more so than drawings. I have set the following 2 windchill properties:
thumbnail.generator.extents = false
thumbnail.cadagenttimeout = 10800
I have also set adapter/useMinMemTriCount to a very large number in thumbnail.rcp. From PTC Tech Support about adapter/useMinMemTriCount:
"In Creo View Adapters CAD model geometry is interpreted as triangles count.
Out of the box Creo View Adapters are configured to use Minimum Memory for thumbnail generation when count reached 5000000.
In our case as a workaround we are increasing this triangles count to 15000000 so that it will not go for Minimum Memory consumption (RAM) mode during Thumbnail generation.
During in-house testing I am able to generate thumbnail in about 20-30 minutes with modified value where it took hours with default value."
So basically this controls how much memory pvsthumb.exe can use when creating thumbnails. Upping this (if you have the memory) will greatly speed up thumbnail generation. My proe2pv.rcp file. Note how it includes the thumbnail.rcp file:
======================================================
file=proe2pv-rcp
ver=5
lastp=gen
adapter/outputAuthorState=1
adapter/outputGzipDWG=1
adapter/outputDatumCurve=1
adapter/outputAnnotPlanar=1
adapter/outputAnnotFloat=1
adapter/outputAnnotScreen=1
adapter/useTransparency=1
adapter/regenerateModel=1
adapter/regenerateDrawing=1
adapter/pdfFontControl=1
adapter/pdfUsePenTable=1
adapter/useTexture=1
adapter/serverVersion=1020
adapter/proeCommand=c:\/ptc\/creo3.0\/Creo 3.0\/M120\/Parametric\/bin\/cp_fv.bat
adapter/timeoutShortHelper=4800
adapter/timeoutLongHelper=5400
adapter/plotter=cadworker_color
adapter/sourceOutputRemove=1
adapter/thumbRecipe=C:\\home\\cadwrkr\\thumbnail.rcp
adapter/useHelperRestart=0
adapter/abortErrorList=56290
adapter/failErrorList=56123 56125 56328
adapter/outputPView=1200
======================================================
And my thumbnail.rcp file:
======================================================
file=pvsthumb-rcp
ver=5
lastp=gen
adapter/createSubModel=-1
adapter/useMinMemTriCount=1500000000
adapter/outputPView=1100
======================================================
Screenshot of the pvsthumb.exe that creates the thumbnails on the cadworker: