Settings > Switching Desktops > Monitors. Exclude the monitor on which the single application is supposed to run. The desktop slideshow will then only affect the other monitor. Is that what you had in mind?

Is it possible with an additional program like DisplayFusion?
I'm looking to have an application run on one monitor and a desktop slideshow run on the other monitor. Can't figure out how to do that.

Thanks,
Bas

The "different background image positioning" part is possible, but not the rest.

I'm using two monitors and I want to be able to play a fullscreen program on one monitor and not be alt-tabbed when clicking on the other monitor. I'd also like to be able to have different background image positioning on the two monitors (for example "stretch" on one and "fit" on the other), as well as have two separate alt-tabs on them. Is any of that possible with dexpot?