I do have photoshop, so I usually just use that to import images to paintshop by the kludge of copying the opened image and pasting in the paintshop workspace, because photoshop still annoys me after all these years. But for other people, I think that a transparent PNG ought to work -- since it is what SimPe exports as, they're very likely to be using them at least part of the time anyway.
Thank you for this cutie!