Options for hanging prints on the wall?

I recently bought a Canon pro-500 (pro-1000 but for Asia) and I've been experimenting with different prints. I'm getting up to a quality level I'd like to hang on yummy wall and I'm looking at options for mounting.

Where I live it's easy to get Fomex and hardboard, but gatorboard and dibond are hard to get--I might have to ship them internationally.

I'm ok to start with fomex, but I'm interested in putting an additional frame behind it to make it float off the wall and allow me to mount it on screws rather than Velcro (I've got wallpaper). I've heard about doing wood ferrings and gluing them to the back, but I also saw something once about specialized metal frames that would keep it from warping and also make it easy to mount over screws.

Does anybody have suggestions for the best ways to mount photos like this to the wall? I'm printing on fine art paper and mounting it to the backing material after printing. Sizes are from A4 to A2. I'd like to learn a technique that would hold up for larger prints as I might get a 44" later on.