As an artist, I like to see how other illustrators and and visual artists create. That includes learning what their studios and workspaces are like as well as seeing how their sketches and ideas take form and evolve. In many ways, images of works in progress (WIP) can be even more interesting than the final drawing or painting.
So, every so often, I'll share some insights into my own work.
The drawing for my Bass T-Shirt began with a simple thumbnail sketch.

The key elements at this point were in place—the jacket hanging off the shoulders, and the bob cut.
Once the initial concept was down, I sketched it again but paid more attention to the overall balance of the figure.

Now it's starting to resemble the finished illustration. At the point, I liked this rough drawing well enough that I decided to turn this into a finished piece. In order to get the proportions and pose right, I drew yet another version.

First came the basic parts in black. The it was on to the jacket in pink and some of the details of the bass in blue.
Once that was done, it was on to the final version.

You can see that while drawing the final version, I changed the shape of the bass, fixed the posture and positioning of the hand on the neck, and added the frame.
This graphic tee design is also available in Pink and Green.