Is it possible to change the Default Tool for the file that gets saved to something else, a picture viewer for instance?
Of course: Personal Paint takes this data from a reference icon stored in the local “PPaint_Icons” drawer. Just change that icon. There is one for pictures, one for animations, etc. Alternatively, you can leave the preset “PPView” Default Tool, and reprogram PPView to use a viewer of your choice by using SetPPView (“Utilities” drawer).