Is there an easy way to make a part of the background be "behind glass", and characters, objects, etc. moving behind the glass will be tinted in some grey way (or similar) to show they are behind the glass? Is it also possible to tint the background in the same shade, if it was drawn as if the glass wasn't there.
You could possibly use a region and use the Colour Tint settings to change the character colouring. Not sure if it works for backgrounds and objects, though - you'd probably have to import them re-coloured.
A simpler way might be to make the 'glass' an object, and alter it's opacity (Object.Transparency) to make it semi-transparent. Dependng on exactly how the room's set up, you might also have to play with the positioning of it's baseline, whether it can be clicked (Object.Clickable) and/or a walkbehind (e.g. if it's a window in a wall).