The 2D artist known as Reverend did a design based on a small colony ship only partly seen landed and overgrown with vegetation in the DS9 2nd season episode "Paradise". Not sure if those images are still out there, but I have some saved. Give me a shout if you want em.
Also, back in 2001, physical modeler Michael Bower Putman, aka Feyman Shipyards, kitbashed a cool 3-stage colony ship from assorted parts. His site is here