I love Google SketchUp, and although it's one of my enthusiasms I haven't mentioned it yet. I don't have the time, money, or space to start building my tiny house, but I can mock it up in SketchUp!
At the left I have the floor framing - the indented bits are where the wheel wells of the trailer stick up into the walls a bit. I left the standard Google character in for an idea of size, but it's roughly 7' by 18'.
And here's flooring laid. There is 3/4" plywood on the right to go underneath linoleum for the kitchen and bathroom, and since I'm dreaming big here, there's 6" wide reclaimed Douglas Fir planks on the left for the living/dining/everything else area. The plywood texture is built in to SketchUp, but I used their "create texture" option to paste in a photo of floorboards which it used for the flooring. It looks a little odd, but gives an idea of the overall colour, at least.