You know icons8.com, right? So, I was using our website to generate logo concepts: to search for a topic and check similar icons — this way, you could get lots of concepts (good, bad and horrible) in couple minutes. So we've built this functionality into the app, and here I've published a small instruction.
I beg your pardon if Similar icons works strange in rare cases; it's a very new feature and we need couple updates to make polish it.