I am currently cleaning up my laptop, freeing it from the virtual pictures I gather. I don't know what your criteria is for saving an image, mine is simple, if I look twice and swoon a little then 'bang', into the files it goes. So, as a result, I have stacks of pictures completely unrelated.
However, I have noticed that I love images of similar things grouped together. Everytime I'd come across a picture of like-items in a group - during my 'clean up' session - I'd let out a deep sigh! I'm a bit nuts like that...here is a tiny sample.