I like the image: it's very fluid and the shift in scale brings a lot of interest to the figure. The gun belt is especially appealing! However, I think it looks a bit awkward on the shirt; it's kind of crammed into a corner. Perhaps if you separated the figure from the sun and then added a long/extreme shadow you could bring some of the image's fluidity to the shirt's layout.
Also, you might chose a sand color for the shirt itself, to invoke the desert.
About my design
to alone,when he broken,when he tired
or when he is in love.In my design
now the cowboy in boring day :)
have a good day,cowboys!