There is somewhere a pdf "The book of bad ideas" not sure if it was on this forum, i dont want to look for the link now.
Also watch lots of videos, i would suggest Make Noise, Monotrail, Undulations (allthough he does not mainly Eurorack but definitely helps you to think out of the box like clocking a sequencer with an audio signal from playing piano or clocking it at audio rate and using as audio source and gazillions of other weird ideas of abusing stuff)