Okay, story time. When I was younger, I had a lot of anxiety problems, so I made symbols with my hands to calm myself down. I came to really like the symbol of a bottom-heavy diamond with a smaller diamond beneath it, so I doodled it a lot. When it came to have to represent myself, I decided that that symbol would be fun.
I also really like really, really tall towers. So I stuck that symbol on a tower, added a cloud background and birds, and called it my icon! I've had it for several years now. Paul's Tower, which is also what I usually use for usernames.