I have made a skybox collection.
6 images on a cube for backgrounds

What is a skybox -- description at wiki-
http://en.wikipedia.org/wiki/Skybox_%28video_games%29

I made them in .obj and also .x format with the textures being .jpg, 1024x1024 boxes and .jpgs, boxes are reversed normal boxes and also boxes made from 6 sheets to make a box.

I want to maximise my sales, I know poser is a very popular application, I would like poser users to be able to use my skybox collection.

Do my models have to be in a special format for poser, If so what is the file format?
Is there anything I need to know about saving to a format for poser users.

I don't use poser so I'm presuming I just output my files to a format compatible to poser and that's it. model file and the texture file in a format poser likes and that's it. Is there anything else I should know.

Also Daz studio, does that use the same formats as poser

Poser likes .OBJ files better than other basic mesh formats, but you'll
sell better if you rig them as figures (CR2 files).  If you don't have Poser, maybe
you can get someone to do the rigging in exchange for a free file.  

The best and most succesful vendors around here tend to be those whom take hands-on approach to Poser.  Most of them have started off with making a few freebies first to get the feel for the market and what it takes to create a poser friendly item.
Also, look at the products you may be competing with, for example, 'cycloramas' and skydomes.

For example, a cyclorama is very similar to a skybox, and something many poser users are familiar with. There's a pretty decent number of free textures available for it: http://www.renderosity.com/mod/freestuff/search.php?section_id=-1&query=cyclorama
and in marketplace: http://www.renderosity.com/mod/bcs/index.php?Start=1&SearchTerm=cyclorama

My files are .obj so I poser should be able to handle those.
Figures, crt files. These sound like files used for a poser model, i.e. a figure, is that a good file type for something that isn't a figure, id say these skyboxes are more like props, not sure what format the poser props are I have seen sold in many places.

My skyboxes are all boxes, they may need changing in size inside the application, say poser in this case, does poser handle changing model sizes, from what I remember of poser from years ago is that it just made or altered figures/characters, though Im sure it is capable of much more these days, I know that it has been updated many times and given many new options. I also see that Daz studio is very popular, what's the file format with that is .obj fine or does it like something else.

Thanks for the links, Id say my products compete very well with the ones show both in quality and price. Hopefully poser users will be interested in my product and use them to create fantastic art pieces.

Cyclorama, is that a part of poser, i.e. a program with poser, I did a search and couldn't find a download link so Im thinking it could be an application with poser.

Perhaps this is it and its sold separate
Daz Multiplane Cyclorama
http://www.daz3d.com/i.x/shop/itemdetails/-/?item=651

What exactly is Cyclorama?

I wouldn't buy a cube mapped with a sky texture, but poser users will buy almost anything. however, it seems like mapping onto a skydome would be alot smarter IMVHO.

yeah a skybox is not really the way to go for poser as you need to be able to do even lighting, and it would be pretty difficult to light a box evenly enough in Poser. a skydome would be more popular. and yes it should be in a prop format .pp2 but frankly if you didn't include a light set to properly light it Im not sure how many bites you would get. No offense but it really doesn't sound like you know enough about poser to do well as a poser merchant. you should learn the software before trying to market to people who use it.

Yeah, and most of the average poser users don't like to import OBJ's, especially since it often means that the textures need to be imported separately, through the material room.
Most of the users that knows how to do thid know how to make a skybox too, and most of those whom don't, will get very frustrated.
At the minimum I would package the skyboxes in Poser native format, so they show up on poser content menu upon install, rather then the obj's that need to be imported.

You'll often see many poser users pass up a freebie because it's in an obj format that needs to be imported.

Not to say that your product isn't any good, it's just that the poser content buyers have rather specific needs and interests.

Also, when talking about skyboxes, poser has the ability to render something against a background image, which is a little like a built in skybox.

These are the skyboxes.

http://www.avantivita.com/ootb_skybox1.html

http://www.avantivita.com/ootb_skybox2.html

Would Poser users be interested in this type of thing, perhaps I could get a poser user to make them poser compatible and Ill give them the skyboxes for free for doing it for me.