Bunnings has real cheap carpet squares that would cost you about $400 to do a double garage size floor.They have lots of colours, but black or dark grey is best for obvious reasons.They come in a small box which holds ten squares.
When i went to my local bunnings, I asked the manager "if i buy 20 or 30 boxes from u guys instead of the local carpet shop", would you give me a discount??....the manager gave me another 10 percent off and my garage came up a real treat.
Your shed looks great.Job well done.