hahahah... that's up to your creativity and imagination, and again using your observational skills. don't take things literally, eg. must be a picture with ripples in it, ripples must be made by water, etc. you can have pictures that infer ripples. not only water makes ripples, patterns make ripples...
these pictures can be created by yourself, meaning posing objects against other objects or using light/shadow to convey the idea. Or if you notice a particular scene which would suggest such things... i'm being very vague here because anything can happen and anything can be done. your brain's the limit.