Me bad.
My description wasn't detailed enough.
@RandomCoder, your hints are already used in my code, the only thing I'm not using is the changing of folders.(The naming convention is more like acespade.gif, 2spade.gif, ....kingspade.gif,...)
My question in more detail:
How do I make my application use files that are being saved by the user (using other tools) in a specific folder?
Is it even possible to use a folder directly accessable by the user? Or should I copy the (user-declared) folder holding the images to a application specific folder?