If you want a rather good option for carpets that both tends to look good and is easy to use, look for the adhesive backed felt sheets at craft stores. A lot of color options, stuff doesn't end up as fluffy as normal felt, and it's rather simple to cut it, peel the back, and push it in place.
You can also do some decent patterns with it for various carpet patterns if you want to take the time to cut the pieces out.
Used some for it when a friend was setting up a small town board with an old motel for part of it.
Stuff is also quite cheap to get, $0.15 for a sheet close to the size of a standard printer paper (Same size the craft foam and similar things some in).