I'm giving up...
tried scraping again but the entire downloaded_images folders are filled with those Flashback templates and none of them are from the actual games...
I deleted my settings and tried again, same issue.
@CaffeineFiend: It is actually possible to add the roms directly with the SD card put into your PC but it's not a trivial task. You have to mount the right partition to make it work. Using the browser or the network share in your file browser is the much easier and preferable way to do it.