in windows, you can find the actual PNG generated by the game here:

C:\Users\YourUserName\AppData\LocalLow\Koan\SketchCrawler\account\skins

i ignore if each save file generates two folders here, since in my case, i only have one save file and two folders are listed here. The first folder has another subfolder named "cards", and inside are other folders which contain the pngs.

* you may need to manually write the address, because "AppData" folder may not be visible.