Thanks: I did the job using a facility in P3dO Explorer.

When use of .png instead of .rsr as Poser library icons was new, Poser automatically converted any .rsr to .png in any library folder that it looked in; that was useful. But this does not happen now; I have an old character called Millennium Horse SR1, with files Millennium Horse SR1.cp2, Millennium Horse SR1.png, Millennium Horse SR1.rsr. I renamed Millennium Horse SR1.png to Millennium Horse SR1xxx.png, and then looked at that library entry using my Poser 10, and it displayed as the "No Preview" "shruggy man" image. I then renamed Millennium Horse SR1xxx.png back to Millennium Horse SR1.png , and refreshed the library display in Poser, and the icon for Millennium Horse SR1 went back to a brown horse's head and neck, as it should be.

Please tell Poser's current maintainers to restore the ability to automatically convert .rsr into .png , as likely there are many old websites of Poser characters (including old long-standing Renderosity members' old freeware and marketplace ware) which still have .rsr and not .png as the library entry's icon display.