Don't know if this has been tried yet.  But I'm pretty close to making a "working prototype" (I just need to find and print out some decent masterboard tiles), so here goes:

Step 1: Create the magnet "mounting points".
You can do this with bits of wood, but I went for the all-paper version.  Let's see if I can explain this properly without pictures.  I cut a strip of paper, which has the length of an A4 piece of paper, a width of about 5 to 7 mm (one 5th of an inch), and which weighs 200 gr/m2.  Then I "roll" it into a "ball": imagine rolling up a poster, but instead flatten the paper with each "roll".  This will give you a niche, thick, solid mounting point (obviously, you have to use glue at the end to prevent it from "unrolling" again.

Step 2: Glue the mounting points
Simply glue any number you desire on the inside of a prop/wall/... all the way at the bottom, so that one side of this mounting point touches the table surface when you put the prop down.

Step 3: Glue magnets to these mounting points.

What follows now, I haven'tr tried yet, but I will probably before the week-end.  I'll let you know the results.

Step 4: Build the masterboard floor tiles.  I suppose you can do this with sheetmetal (used to provide statues etc. with a thin layer of silver/gold/copper/...), but I went for something a little more sturdy: a metal mosquito net.  It's quite flat, light, and thin.  Here's the plan:

1 layer of foamcore.
1 layer of mosquito metal
1 layer of masterboard printout, on 120 gr/m2 paper
1 layer of clear matte protecting plastic (self-adhesive).

My tests so far have been promising: the props stick to the metal with their magnets, even when I put some 200 gr/m2 paper and plasting in between, and they come loose again very easily.  When I shook the metal net, the props seemed to remain in place very well.

BTW, you can also glue these magnets to the bottom of your miniatures.

Hope this helps and gives some ideas.  I'll fill you in on how it works out.

Sounds like a terrific project Dicelot! If you have the means try and take some pictures of your work so we can all see what youre up to.

Welcome to the forum

Thanks!

I think I'll be able to get my hands on a digital camera, but it may taka a short while.  In the meantime, I've bought GothicRealms from RPGnow, and it looks promising.

That sounds particularly interesting. I was thinking of trying the same thing, only using magnetic tape on the models (and doing the same for cardboard counters). Where did you find the metal sheeting to use?

Actually, I tried with an iron mosquito net (more like a grating) today.  It doesn't work, as it proves too difficult to cut into pieces of the right size.

I'll be visiting a hardware store (specialized in metal) tomorrow to see if they have any sheet metal, or anything that can substitute (I guess they'll be able to cut in to the right size if needed).  There's also a few shops on the nternet which seem to sell this stuff.  Try the new Froogle service from Google to search for them.

I'll keep you posted on any progress I make.

If you look hard enough, you can find "paper steel" Its very thin sheet metal sold in 8 1/2 X 11 sheets, that you can cut with a pair of sisors.