Personally I think the most impressive thing here isn't that you created a self-driving MarioKart, but that you trained TensorFlow based on input screenshots of your desktop.
I feel like that could be a good next step - a ubiquitous neural net model that, after mapping inputs, will learn to play any video game that's on your screen.
Especially since the hard work of increasing the screen resolution has already been done.
Also, bravo on including the stupid little bugs that gave you trouble. It always sustains me working on a hard project to know that a self-driving video game was blocked by a missing newline in a C HTTP request. It makes me step back and laugh at the ridiculous complexity of what we take for granted in our day to day work.
I feel like that could be a good next step - a ubiquitous neural net model that, after mapping inputs, will learn to play any video game that's on your screen.