I don't know why I never thought of this myself, but it's such a great idea I wanted to share it with you! I don't believe it reinventing the wheel, so I'll just direct you over to Thrifty Decor Chick, where like Clarissa, she explains it all.
But basically, you can create your very own subway art printable using a blank document and the free photo editing website Picnik! Brilliant, right? So I made my own!
My favorite "style" if you want to call it that have been of the street name variety! Here's my version that I whipped up in just 15 minutes...
This was so easy to make and I love the pop of color it adds!