Try these foam mats, from Harbor Freight: link. They are $6.99 USD for four, with a coupon. The "top", is made with a diamond pattern, and not usable. The "bottom", however, is smooth. It takes craft paint really well, especially with a wet, natural sponge. Others have used latex paint, but I prefer acrylic, less chance of peeling.
If you need water, apply 2-3 shades of blue, green, and white, applying immediately, so they intermix nicely. For grasslands, use 3-4 shades of green, brown, yellow, maybe a little purple. For snow, base coat in white, then sponge on some blues, and paint on silver glitter glue, to give it some sparkle.
They can be painted to just about any type of terrain. Very affordable, very easy to use. Lightweight, interlocking, easy to transport. Cheers!
