Your samplers are just recorders. So you have to make the new sound with some other device that you sample into your samplers and then use the samplers in a live or studio performance situation. The good thing about this is you have the flexibility to create new sounds from anything and everything.
One thing you can do is make new sounds with various physical objects. A hand saw is the classic example. Anything you can get your hands on and bang together or wave through the air or hit against something can potentially create a new sound that you can sample into your samplers, spread and/or layer across the keyboard, and create a totally new sound.
Another idea is to rent various synthesizers from a musical instrument store, say for a month at a time, and work with those synthesizers to create new sounds and sample those sounds into your samplers.
Same goes for apps on a Mac or iPad or PC. If they generate some kind of sound, you can sample them in your samplers.