VCT (or vinyl composite tile) flooring is cheap & hard-wearing
via Make leather look floors using Paper bags! Cool cheap DIY idea for flooring - paper bag floors. They look like leather
Do-It-Yourself Laminate Flooring: Lay Planks Out "Dry" First
I like the idea of laying down an insulating layer between the carpet tiles and the concrete floor. I want the basement floor to feel insulated and warmer than just carpet tile on concrete.
Installing stick-down laminate tiles in a bathroom - easy to stick, easy to cut, and this link includes a little tip for how to custom-cut curved edges (like around toilets, sinks, etc.) **For upstairs bathroom