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For the spell Programmed Illusion, is there a maximum volume? Minor Illusion can go as high as a scream, which is only a cantrip while this is Level 6.
Would it be possible for Programmed Illusion to deal thunder damage or, similarly, be bright enough to blind someone?
In 5e, spells do only what they say they do by default and the DM must make a ruling for any effects or interactions beyond that. Illusion spells especially are notoriously open-ended and subject to DM interpretation.
The only description/limitation of what effects can be generated are explained in the first part of the spell:
You create an illusion of an object, a creature, or some other visible phenomenon within range that activates when a specific condition occurs. The illusion is imperceptible until then. It must be no larger than a 30-foot cube, and you decide when you cast the spell how the illusion behaves and what sounds it makes. This scripted performance can last up to 5 minutes.
Programmed illusion simply does not specify if it can do any of those things you ask about. And different DMs have different ways they have illusions work in their world therefore ruling will differ from table to table.
At my table, I would be very leery at allowing a spell which does not impose any conditions or do any damage to do so. Or at the very least, not more than once for a Rule of Cool moment. Illusions can already be extremely potent weapons when used in clever ways with a permissive DM and allowing them to cause physical effects only makes them more powerful.
Allowing this also opens up a lot of headache for questions like "how much damage?" or "how long are they blinded?" which can add complication to a spell which already is fairly complicated for a DM to adjudicate.
If your DM wants to allow it they are more than welcome to at their table, but my advice would be to bring it up with them before attempting it to avoid a possible disappointment and to keep the game running smoothly.
Yes, because illusion will make victims of the spell think that it's a true thing, so their mind will make them fill it (so they will be blinded by a too powerful light made by the illusion, they will be hurt, as psychic damage, if the illusion "hurt" them one way or another, etc).
And no, because if victims know that is an illusion (saving throw, Intelligence check, etc), it will do to them nothing (maybe an illusion that make deafening sound will make them not hear anything else but that all), and unreal damage could disappear (at least thing like blind, deaf, paralysis, etc).
The only way that illusions can do real damage is if they are shadow spells (for D&D 3.5e, not sure that it exist in D&D 5e) or if victims believe so much in the effect that it appeared one way or another (like Phantasmal Killer).
I base myself on the second part of Phantasmal Force's description (PHB, p. 264), because it make sense that it's the same for other illusion spells:
While a target is affected by the spell, the target treats the phantasm as if it were real. The target rationalizes any illogical outcomes from interacting with the phantasm. For example, a target attempting to walk across a phantasmal bridge that spans a chasm falls once it steps onto the bridge. If the target survives the fall, it still believes that the bridge exists and comes up with some other explanation for its fall—it was pushed, it slipped, or a strong wind might have knocked it off.
An affected target is so convinced of the phantasm's reality that it can even take damage from the illusion. A phantasm created to appear as a creature can attack the target. Similarly, a phantasm created to appear as fire, a pool of acid, or lava can burn the target. Each round on your turn, the phantasm can deal 1d6 psychic damage to the target if it is in the phantasm's area or within 5 feet of the phantasm, provided that the illusion is of a creature or hazard that could logically deal damage, such as by attacking. The target perceives the damage as a type appropriate to the illusion.
I would do this way as a GM because their is no clear rules about it (as far as I know, I might be wrong).
