... You would think that an office cubicle would be pretty easy, but the devil is in the details. As in how much detail to include...

So the dilema is, so do I need to worry about showing support structures, like brackets for the desk and shelves.

Here's a rule-of-thumb for geometry/polycount: Always model for "intended use."

For instance, let's say you're modeling this cubicle and it has some cabinet doors in it. The cubicle is designed for decent resolution renderings and for certain sorts of closeups suitable from a character's normal point of view.

So, do you model the hinges for those cabinets in high detail, complete with pins, screws, etc? No, of course not! Nobody is intended to use this entire model just to do a closeup of an ant walking over the screws of one of the cabinet hinges, so that sort of detail isn't necessary. Whenever you're modeling, decide in favor of modeling for "intended use" and don't hinder the user's use of the product for "intended use" by constructing additional geometry that isn't focused on that use. (ie: You wouldn't model things inside the cabinets if the cabinets were not meant to be opened. :) )

Poser also has certain construction requirements and that should be your primary concern regarding geometry. For instance, Poser has certain requirements for objects. See Product Guidelines, here: http://www.renderosity.com/news.php?viewStory=13759 (I think DAZ might have a more technical one, can't remember.) So, when you're constructing specifically for Poser, there are things you have to do. This will determine what you may have to do using other means!

For instance, the walls of your cubicle - How many polys? (Not sure if that's a wire render or not, don't know Blender.) Let's say that those individual walls are only six polys, the minimum needed for a square. If that is the case, then you are not going to be able to apply smooth shading effects to them without Poser distorting them in renders. To keep this from happening, sometimes objects are created with split vertices, to halt smooth shading effects. BUT, that causes havoc in Poser with displacement mapping and certain sorts of materials, so split vertices are highly undesirable and nobody will accept products for sale for Poser if they contain them. Let's say you intend this product for medium distance renders, like what someone would see if they walked by the object or were sitting at the desk. Well, you can't ignore smooth shading effects if you want a realistic looking cubicle. And, let's say you want some displacement mapping, as well. What are your options? You're going to have to chamfer the edges of those six-sided rectangles that make up the wall portions of the cubicle. That will allow smooth shading to be used, depending upon the angles and a few other factors. This will result in a product suitable for good mid-range renders and also affords you the ability to add some details, using the same construction principles, without smooth shading effects tearing them up to pieces in the final renders. All objects, regardless of how insignificant they are, need to be treated the same way for Poser. Even a tiny little rectangle representing a hinge will turn into a blob in a Poser render with smooth shading effects on and no edge chamfers, which the smooth shading calculations need to keep from distorting even that tiny bit of geometry. But, chamfering the hard edges of such objects does happen to increase their geometry and the overall footprint of the product.

Textures/maps vs geometry

I think the first rule to remember is - What does your chosen rendering engine need, what can it use and how does this effect the intended uses for the product?

Do you need a separate one-face plane in order to represent a piece of paper taped to the wall of the cubicle? Maybe. Certainly, for medium renders, you would. Otherwise, shadowing effects wouldn't get calculated for it and that would ruin the realism. Also, the render wouldn't show it as being separate from the wall geometry and you can not do that with displacement effects. So, yes, for your "intended use" you must have a separate image-plane geometry for that one piece of paper. And, since it's for a medium render, you probably also need to be sure that the text on that single piece of paper is legible in a render! What does that mean? That means that the size of the texture image for that one piece of paper may need to be significantly larger, in proportion, to the size of the texture that represents the fuzzy carpet-like covering on the wall of the cubicle portions.

When creating textures, you texture at the resolutions that suite the intended use of the product. For instance, the texture for the tacked-up office memo may need to be 500x500 at the very least, so that the text can be somewhat read at medium render resolution. However, the texture for the individual wall portions of the cubicle may not need to be over 1000x1000, since they don't have much detail at intended rendering resolution levels. But, we see that the memo only occupies less than a tenth of the physical space of a wall portion, yet its texture size is half the size of the whole portion of the wall! Why is that? Intended use mitigated by footprint necessity and efficiency, that's why. :)

This applies to the geometry vs texture debate because you always have to balance the two with your primary goal of a product's suitability for "intended use." Everything you do should be focused on that. This includes opting to use displacement or bump maps instead of geometry. Which serves the intended use better and what extra additions to the product, to help with other uses, do not unnecessarily hinder intended use?

You know the basics of displacement and bump maps and what they can and can not do. So, there's no reason to discuss that. You have to weight what you know about the technical aspects of Poser and what you assume your users will want to do with your product, balanced against the product's intended use, in order to make the right decisions.

On materials - Poser has a strong material room, so don't forget that in your calculations! Besides displacement and bump mapping, you have all sorts of surfaces you can create and lighting effects to mess with. I don't know it well enough to give you a definitive rule-of-thumb, but I'd say that for any surface, you can reasonably expect to let Poser handle the "general" materials for that surface, including generic details, that are repeatable or random on that type of surface, with materials. Versatility is key, though, so you should provide good UVs that allow your users to use textures appropriate for intended use. (ie: You can make separate groups for all of the screw-heads in your model, for instance, and provide a tiny, itty-bitty, UV space for them, if you wish. But, in your release version, you wouldn't bother doing anything more than just providing a decent material for them and, perhaps, a grey splotch in your texture map. You wouldn't provide a texture that shows the tool access for the screw, since that would take up far too much UV space when considered against the product's intended use.)