About the logo- it should look like something that can be printed on a shopping bag, or something that can be made into a neon sign. No textures or gradients, just solid colors. Where gradients would be useful is on the walkways, to make a smooth transition from one color to another. You might want to put an asphalt texture on the gray outside and drop the gradient, so it looks like a real parking lot. And if there's anything you can do about those pixel people, please do it.

I'll comment on gameplay later.
