Speaking of Polyrythms, the new melody sequencer mode for the Push is BUILT for producing them. You can construct rhythmic sequences and then just keep altering step lengths and adding new tracks.
I really love Recording loops from synths and samplers into session view and getting into a groove and producing 5-10 new takes on what I’ve just recorded is pretty inspiring.
I think my pure music suggestion is getting your hands dirty with your percussion and throwing together some pad sequenced stuff and keeping it in a folder you build over time. You really get intimate with each little hit and really hear what’s happening to it in the mix when you’ve built it from chopped samples and filtering/FX or carefully selected one shots.