I'm trying to figure out the difference, especially in the context of using one of these spells to conceal a campsite from casual observation by creating the illusion of a pile of rubble from a wall (not necessarily with creatures present at the campsite).
I'm thinking you need Mirage Arcana. Permanent Image/Silent Image will create a pile of rubble, but I don't think they let you conceal things with them (who needs Invisibility if they do?) or make your campsite look like something else (see Figment).
Hallucinatory Terrain is natural terrain only so that won't let you make rubble from a wall. On the other hand, I think it would work if you were creating a grassy field to hide in (probably requiring you to make a Hide check as per Mirage Arcana). This is also a Glamer spell not a Figment.
Mirage Arcana is a better version of Hallucinatory Terrain that also lets you creature structures, so rubble of a wall would probably fit here. Also, creatures within the campsite could make Hide checks to hide within the rubble.
Does this sound right? Thoughts?
Permanent Image: This spell functions like silent image, except that the figment includes visual, auditory, olfactory, and thermal elements, and the spell is permanent. By concentrating, you can move the image within the limits of the range, but it is static while you are not concentrating.
Silent Image: This spell creates the visual illusion of an object, creature, or force, as visualized by you. The illusion does not create sound, smell, texture, or temperature. You can move the image within the limits of the size of the effect.
Figment: Figment: A figment spell creates a false sensation. Those who perceive the figment perceive the same thing, not their own slightly different versions of the figment. It is not a personalized mental impression. Figments cannot make something seem to be something else. A figment that includes audible effects cannot duplicate intelligible speech unless the spell description specifically says it can. If intelligible speech is possible, it must be in a language you can speak. If you try to duplicate a language you cannot speak, the figment produces gibberish. Likewise, you cannot make a visual copy of something unless you know what it looks like (or copy another sense exactly unless you have experienced it).
Because figments and glamers are unreal, they cannot produce real effects the way that other types of illusions can. Figments and glamers cannot cause damage to objects or creatures, support weight, provide nutrition, or provide protection from the elements. Consequently, these spells are useful for confounding foes, but useless for attacking them directly.
Mirage Arcana: This spell functions like hallucinatory terrain, except that it enables you to make any area appear to be something other than it is. The illusion includes audible, visual, tactile, and olfactory elements. Unlike hallucinatory terrain, the spell can alter the appearance of structures (or add them where none are present). Still, it can't disguise, conceal, or add creatures (though creatures within the area might hide themselves within the illusion just as they can hide themselves within a real location).
Hallucinatory Terrain: You make natural terrain look, sound, and smell like some other sort of natural terrain. Structures, equipment, and creatures within the area are not hidden or changed in appearance.
Glamer: A glamer spell changes a subject's sensory qualities, making it look, feel, taste, smell, or sound like something else, or even seem to disappear.