How can I apply contact paper to a concrete floor?

I would defiantly not do it. Contact paper is not strong enough for floor even though I have seen it done. I dont believe it will last. And the second issue you may come across is that it will not stick to the floor properly. Contact adhesive needs a smooth non porous surface to adhere to. Maybe look for another option in my opinion.

That sounds very fun. While contact paper won't be very durable for a floor, but since it's just for you in your personal space, it should be ok. I think you would have to make sure the floor is very clean before you apply. Use some kind of protection for the floor under your chair to keep it from tearing.

Though contact paper is not durable, it comes in a variety of colors. I can see why you would want to try it. Because air bubbles are easily trapped when laying contact paper, it may be a good idea to make contact paper tiles, which would be easier to lay and replace as needed, and use the gray underlying paint as the grout lines.

I would not do that. Poly won't help the biggest issue, which is moisture. Concrete retains a small amount of moisture, as the temperature changes in a basement. That moisture is just bad for the glue. Just paint the floor with a good paint that is made for concrete. You can even stencil it to add a little fun. But I would stay away from contact paper.