In the game I’m running, the PCs are about to embark on a wilderness trek during which they will be harried by an opponent who has access to the major image spell. This opponent seeks to distract, mislead, and delay them, forcing them to spend more time and resources reaching their objective than they would otherwise.
I am trying to determine what is possible within the constraints of the major image spell description. One thing that occurred to me is that, while the spell’s effects are confined to a 20′ cube, they might seem to be spread over a much greater area by tricks of forced perspective. For example, an illusory, 20′ tall castle suspended in mid-air between the party and a distant hill might appear to be a full-size castle settled on the hill. Or a 20′ wide illusion of a wall of flames might seem to be consuming a vast span of the horizon.
Or alternatively, an illusory pit might seem to be much deeper than 20′ by "drawing" its walls and bottom in such a way as to make it seem deeper.
Can forced perspective be used with major image in this way?
Are there potential drawbacks to allowing this? Would any modifiers be appropriate for investigation checks to "disbelieve" them?