Standardizing a format/API upon a tool like SQLite was something that was proposed in the web world as WebSQL but scrapped due to not wanting an entire standard to rely on a specific code base but rather wanting to have the standard be possible to reimplementable by others and thus creating the IndexedDB standard instead.
I'm not proposing that an image format like this one should use IndexedDB, but if relying on SQLite means being reliant on a specific code base that has to be used by anyone that wants to read the file - then it's probably not such a good idea.
When discussing this I think one should also have in mind eg the move to web apps as well - a reliance on SQLite will make it hard for them to read the format. A standardized simple base format that can easily be supported in new languages would be preferable as I see it - but I'm no expert in the image processing area.
I'm not proposing that an image format like this one should use IndexedDB, but if relying on SQLite means being reliant on a specific code base that has to be used by anyone that wants to read the file - then it's probably not such a good idea.
When discussing this I think one should also have in mind eg the move to web apps as well - a reliance on SQLite will make it hard for them to read the format. A standardized simple base format that can easily be supported in new languages would be preferable as I see it - but I'm no expert in the image processing area.