After making hundreds of pngs in PSP 7 I may just have to upgrade for the scripting in 8. I haven't got around to it yet.

But in PSP 7 to make a png with a blank background that can be converted to an rsr for Poser 4:

Render a 91x91 tiff in Poser. Open in PSP 7. Go up to load mask from alpha channel then delete the mask and merge with the layer to get a transparent background. Then you must invert the alpha channel by loading the selection from the alpha channel then invert the selection. Next, save the selection to the alpha channel and pick the exisiting alpha channel and it will overwrite it with the inverted one. Next you can add any text you like or logo. Then use the png export option in the file menu. Pick existing layer transparecy for the tranparency option. If you have no text the use the alpha channel option. Then export. For Poser 4 you can then convert with P3DO Explorer to an rsr.