Hi Everyone!
I am completely new to CG and 3D but I’m very keen to get started. My interest though is not in gaming or animation, at this stage it’s just 3D stills.
Could an image like this be created soley in Zbrush or would other programs be needed? 
I am going to hazard a reply. I would say you need more than just Zbrush for such a scene. Zbrush is a modeler and not a scene builder. I would use Zbrush, Silo and Blender for the hobbiest route to that still. Using Blender to set up that scene.
I would disagree and say, of course you could make all of this in Zbrush.
You might have to freehand some shadows, such as those on the walls. You could do it in PaintStop, so yes. If you have Photoshop, then you can blend render passes and freehand for good results.
well then i stand corrected 
Thanks, good to know that it’s possible. Next question, would it be easier to do it combining with other programs and if so, what would the basic workflow be? I read a lot when people talk about their images that they go back and forth with different programs. How do you know when you need to?
I personally think its up to you. If you feel you can better arrange model or get a certain feel or effect from a particular package then you might flow into that package. If you want certain backgrounds and terrains, you might choose a package that can do that. I personally use VUE often. I will model objects and figures here, then import them into VUE for scene arrangement. I know i cant get vast rolling landscapes out of Zbrush. thats not what its built for. Zbrush is a modeling program. I also like Silo, It has easy scene navigation but cant truely render. So, If i wanted a more complex scene I would model and texture objects in Zbrush, Import them into Silo, layout the Scene, Build architecture (silo dose this well) then Import Scene into a render Package. Messiah, PovRay, Blender. I list Blender as a Render package, but its more than that. If you haven’t tried Blender i would recommend it, its a great Modeling-Animation-Render package for free. Its open source.
A rendering Program allows you to set camera angles adjust lighting, add specular effects like fog rain dust. They also handle animation. Rendering is the final time you handle the art assets of your project. Next would come sound if you were doing an animation. Then again Some do sound at the animation stage along side it.
sorry if this was TMI, but the world of CG is complicated.
I use modo 401, a great compliment to ZBrush and from another great company. Yes, using a 3d package such as modo will improve your workflow and allow for more realistic renders in many cases. You should do it if you can.
I use modo for some base meshes, hard surface modeling, materials, scene set up, and rendering.
ZBrush rendering and scene set up is powerful though, just different. Sometimes it will be the best route. Learn render passes, the basic material modifiers (not matcaps), and the power of the 2.5d canvas. You could easily create a scene in ZBrush that no 3d software in the world could handle. Likewise, you could create a scene in modo that has light, shadow, and materials that ZBrush couldn’t produce. So it depends on what each scene needs to be effective.
This is a link to Meats Meier’s website, where he has posted free training on ZBrush 3.1. Most of which is still relevent. At the bottom of this page is a video on illustration techniques. It will explain the 2.5d canvas for scene set up. Very cool way to work 
http://www.3dartspace.com/index.php?option=com_content&task=view&id=307