What is the maxium amount of pics I can use in a slide show screensaver ?

You can add unlimited amount of pics in theory. But when you add lots of pics (such as more then 5000) to a PSSB project and build with these pics, you will get an output file that has very big size , it runs very slow because it takes lots of RAM. In this case , you can turn to the "output" tab of PSSB ,select the "Local media file" and "Look for media files in runtime directory" build options to create your output file. This type of output file has small size and will look for all your media file in it's runtime directory. Of course , you can also create several output which builder with media files and each of these output file contains not more a certain amount of pics.