I recently finished this Blood Bowl pitch for the league I will soon be running, wittily referred to as Hide Park...
Basic construction was very simple - a 120 x 60 cm plywood board (4' x 2' to our American friends), with a few felt pads on the underneath to prevent it from scratching other surfaces. Everything else is paint, apart from the static grass tufts.
I started by painting the 'grass' area of the pitch a medium brown, then stippling lighter shades over it using a large paintbrush in an approximation of the colours I use for my grass based figures. A tutorial on this can be found here: Temperate Grasslands Basing Tutorial.
Once the pitch was completed, I covered the rest of the board in a medium grey, and marked off the large stones with a darker shade, which took an age to do. Then I started mixing small amounts of other colours (largely blues, greens and browns) into the base colour to vary the individual stones a bit.
Finally I painted in the pitch markings in white. I chose small dots to mark the corners of the squares to reduce the visual impact as much as possible, and marked the important lines with solid white.
The final job was to write in all the relevant numbers and letters for the scoreboards, turn marker and dugouts - which I incorrectly wrote as Dead/Injured/Reserves.
Next up, my completed Beastmen team for the league...