Ever since threadless headsets became standard on most new bikes (maybe 15 years ago), headset caps have become a popular way to customize bikes. A few years ago when I needed to replace a cap on my road bike (it broke due to overtightening), I considered some of the options from Purely Custom but eventually just got a plain one. I couldn't think of any text interesting enough to put on a cap, and none of the artwork options interested me much. Heather recently got a new road bike, and I was looking for something creative for her bike on her birthday when I discovered Kustomcaps, which will make a cap with completely custom artwork in addition to various text options. In trying to come up with designs that fit the circular area, I realized that Celtic knots are well suited to this, and Heather happens to be a fan of these type of designs, as she has several pieces of jewelry featuring them. So, I came up with a couple of designs:
These designs were created using Inkscape. The procedure for creating the weave pattern is very helpfully described in this tutorial. Eventually, I settled on the second design, which allowed a little more space to add some text. Here's the result (with a blue bolt to go with it).
I liked it so much I decided I needed one for my own bike. As it happened, we recently made a trip to Ireland, and inspired by the Celtic knot on Heather's bike and my own Irish heritage, I was on the lookout for interesting and unusual designs. I found what I was looking for in the floor tiles of St. Patrick's Cathedral in Dublin.
This was one of many very interesting patterns from that particular floor that we took pictures of. I had to stretch the proportions and add or remove parts in order to get the square pattern to fit a circle better, and I came up with two different candidate designs for a headset cap.
These designs were also created in Inkscape, in this case by importing the photo and using the "trace bitmap" feature to get an outline of the pattern, which then required considerable tweaking. I ultimately chose the second of the two designs. Here it is installed on my bike.
Now I don't think I can go back to a plain cap on my bike.