"Red Dalek, what do you think of my garden?" "Now that the Thals have left Skaro you have really started to break out the seed banks Black Dalek." "Yes. Isn't it lovely Red Dalek" "Maybe we should go and invade something, or conquer some people."
Lovely work, it's sort of got a Frank Bellamy-esque sort of style to it.
The objects are indeed 3D things, from a pack called Swidhelms Alien Flora from renderosity. The render has been passed through a freebie filter I downloaded and installed on Adobe Imageready to convert to an 'illustration' line drawing.