Hi MJ
I have also made Harley T-shirt quilts for my HOG (Harley Owners Group)chapter and a few commissioned ones. Unfortunately I don't have pictures. I really like how you made the blocks all different sizes and shapes.
Unlike you I cut every shirt design out on a 12 1/2 square (12" finished) then put sashing between each square that was 2" finished with cornerstones. The cornerstones were T-shirts that only had a small breast/pocket imprint or the ladies shirts which usually only have a small imprint of the dealership on the back. I designed the quilt with 4 blocks across and 5 blocks down. The inner border was also 2" wide and matched the sashing. The outer border was more of the 12" blocks of T-shirts only with no sashing between each block. I used fat bat batting and tied it because I couldn't imagine trying to quilt through those T's and the interfacing you have to put on them to keep them from stretching out of shape.
I could never find harley fabric either. I think the motor company does not license it out to be sold as fabric by the yard. But motorcycle theme fabric can be found. I have seen tattoos, flames, motorcycles, roadmaps. For my quilt I used fabric that looks like bricks in the sashing because the original factory in Milwaukee is all brick and the color seemed to blend well and not fight with any of the shirt designs.
FF