I love Programmed Image. It is like an contingency persistent image which stakcs with contingency. But I noticed something:
This spell functions like silent image, except that this spell's figment activates when a specific condition occurs. The figment includes visual, auditory, olfactory, and thermal elements, including intelligible speech.
You set the triggering condition (which may be a special word) when casting the spell. The event that triggers the illusion can be as general or as specific and detailed as desired but must be based on an audible, tactile, olfactory, or visual trigger. The trigger cannot be based on some quality not normally obvious to the senses, such as alignment. See magic mouth for more details about such triggers.
The spell doesn't say that you can only have one active in waiting to be triggered. I limit myself to only one at a time to avoid cheese, but the rules don't say you can't stack them. And the material component is dirt cheap, so no limit from this side.
So can you stack multiple programmed image waiting for their condition to trigger? I'm concerned it would be OP if so.