I have had success with wallpaper on foam insulation board, with MDF baseboards glued on, but you will have varied success with that method depending on the insulation board. Some accept the glue better than others. Your styrofoam trim sounds perfect for that. You might try wall paneling as your faux wood flooring. It will give you a very steady base if your floor is carpeted, and it's very easy to move out of the way if you don't need it anymore. You don't have to build anything to use it, but it's more sturdy than just a roll of vinyl would be.
I'm not sure I've seen the wallpaper that you're looking for but it sounds interesting.
I have found the best iron pieces for good prices in Fredericksburg, so I don't have an online source for that. But for inexpensive and basic furniture (not antique, but some classic styles) you might try
Home Decorators... not sure if they have anything you are looking for but I have a settee from them that has held up well and was relatively inexpensive.