Are we capable of using alpha channels for our walk-behind areas? I tried importing a 32bit walk-behind with an alpha but nothing, so I'm thinking not?! If not, does this mean using alpha objects for the blending?
No (not yet at least), walkbehinds masks are just 256 colour images with each solid colour representing one walkbehind area.
Currently you may use a sprite with alpha channel instead but beware that using a large alpha-blended sprite may cause slowdowns.
Only characters, objects, mouse cursors and GUI backgrounds support being drawn with an alpha channel in-game.