I removed the grey fill, some numbers, some lines and added 3 new colours

nice, but I'm thinking it would be cool if it were a schematic for some internal organ (NOT the heart, yawn) - but is this meant to be a dog? Its pretty sweet though.

why would someone buy a shirt that you can't tell what's on it?

That's the point. It's an abstraction. You can't necessarily tell the background from the foreground. and the whole comes from the sum of it's parts. if you don't see it immediately, then I failed in the presentation, and you probably have a weak imagination.

take an intro to abstraction class at any second rate art school, or program, and you will realize that you missed the point. start from square one, say an interesting idea perhaps!