Considering .pspimage files are made and saved in several programs from Corel, and it is likely only these programs can be used for creating of these files. You should be able to use other graphics files (including .png graphics) as resource for .pspimage files.
Convert Portable Network Graphic to Corel Paint Shop Pro picture.
We found 2 software records in the database related to .png to .pspimage file format conversion.
Microsoft Windows software - convert png to pspimage on Windows
A professional photo editor and manager for Windows
Convert from png file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned png to pspimage. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A set of applications used by professional graphic designers