This guide will show you how to preview your model in arma2's renderer, bulldozer.
Bulldozer makes full use of arma2's really neat shaders, looks quite naturalistic compared to other engines/viewers, and is realtime, so shots made with bulldozer would be nice presentation pieces.

You'll need:
-ArmA II (link) <Well worth the $50USD
-BIS editing tools (link)
-A model in 3ds or OBJ format - I find OBJ simply doesn't work but you're welcome to try it.

Optional:
-Diffuse, Specular, Normal textures. These need to be in arma's own .PAA format. There's a photoshop plugin for good boys. It's here!
-RVMATS, what are these?.
Get an "empty" RVMAT here!

Part 1 - Shit regarding textures you need to keep in mind
NOTE: arma2 specular maps are called SMDI, and are set up slightly differently to in other engines. Read "5. Specular map (_smdi)" here.
NOTE: arma2 normalmaps simply won't work correctly unless the filename ends in "_nohq.paa"
Similarly, SMDI maps won't show correctly without "_smdi.paa" at the end of the filename. If your maps look weird, this is why.
NOTE: Applying your shitty little textures to your shitty little model will be a whole fuckload easier if you separate the groups by which texture maps they use. If it's only using one texture map, diregard this.

I'll assume you have the BIS tools installed. There's a tutorial on how to correctly install the tools, i'll add a link when i come across it.

Part 2 - Get the model into Oxygen
Open the "Oxygen" editor. The folder will be called "oxygen 2 personal edition" or something, in the folder you installed your BIS tools. Henceforth we call this program o2
NOTE: if you're using 64 bit windows, it'll be in the same tools folder but within the (x86) folder.

Once in o2, you can import your model via
File>Import>3d Studio...
or
File>Import>OBJ File...

There are problems you can have even after this step.
To check if they've happened to you

Part 3 - Preview the turd in Bulldozer
Click this button:

And you'll get a menu. From that, choose "start/restart"
And you'll be graced by a preview window, using the same shaders and all that as the game engine. It'll take a whole few seconds to get its balls on straight and actually start showing you the model, so be so patient.

Once it's loaded up, hold "numpad +" on your little keyboard there. If you were a clever boy and placed your model in the centre of the scene, it should zoom right in on it.
Now I will make no excuses, the arma previewer is weird and kind of dodgy.
It consistently shows one mipmap level too low with textures of 2048px in any dimension (there might be a fix for that, I dunno) Working with 512s or 1024s she's all good though.