When you look at airbrushed t-shirts, you might want to focus on the basic lines that outline your work. The hard lines should be consistent and sharp.

There is another thing they call overspray. Overspray is a strong indicator and tell-tale sign of how good your artist is or not. Many beginners fall short of mastering their "air" vs. "paint flow".

Shadows on lettering is another thing to check out. How well does a shadow stand-out from the lettering? Does it cause too much confusion amoungst the letters themselves?

Airbrushing is an art. Most artist start their career or this hobby from "fun". Something they saw at a local fair or while on vacation. So they decide to buy some equipment and start fooling around. Once you start, you won't be able to stop. There is a word of airbrush artist out there that take it as serious as their full-time job. It is something that will be mastered if taken the time to learn and understand the foundation of using your tools correctly and the fundamentals of the simplest things such as "color theory".