One possible perspective: thinking of images as a vector space, and thinking of image operations like blurring, sharpening, and even any spatial transformation as linear operators (representable as matrices).
This perspective is most straightforward with a 1-dimensional domain, like an audio signal, or the temperature along a thin rod, because there's a clear way to organize all the values in a vector, e.g. all the audio samples are just in sequence. So if that's appealing to you at all, I would recommend that first. You can do filtering (like with an "equalizer") and add effects like echo/reverb as linear operations.
I think that it is particularly fun to think of some ground-truth signal that is corrupted by an echo in a room and a microphone that attenuates some frequencies, and trying to undo that corruption.