Thanks guys! Ya'll are way too kind.
Svenne: Both of those sound good! The motorcycle being smaller might be easier to finish by the end date though.
Jack: Funny, it's my standard quick, cheap, and dirty base. The rough edges are due to the static grass not wanting to stick to the edges of the base. I thought about spreading more glue there and adding more grass and decided to just leave it.
The base is just Durham's Water Putty, it's like plaster but waaaaayyyyy stronger. It doesn't crack or splinter unless you hit it with a hammer. Shep Paine turned me on to the stuff in his 'How to Build Dioramas' manual. I'm not sure you can get it in Canada, I talked to Bish about it a year or two ago, and they don't sell it in the UK. If you want some and can't get it send me a message and I'll mail you a container.
http://waterputty.com/
I just press the tank down into the wet putty to leave ruts and then remove it and wash the treads off carefully to get rid of the excess putty. When the base is dry I paint it using cheap 99 cent craft store paint a light earth colour. I then add what's basically a wash of darker earth coloured paint mixed 50/50 with water to settle into the low spots. Then a liberal coating of glue and a good sprinkling of static grass.
The tree was added due to Shep Paine's manual again- just to balance out the figures on the other side of the dio. It's made from Scenic Express's Super Trees, a dried weed type paint with lots of branches, painted grey and then a coat of glue and sprinked with their Super Leaf product. It's made for railroading but it works fine for larger stuff.
http://scenicexpress.com/