Constant MAX_IMAGE_BYTES 

pub const MAX_IMAGE_BYTES: usize = 12_000; // 12_000usize

The largest picture a workspace emoji keeps, in bytes, once made small (EmojiSource::add makes it so): it travels inside the action that adds it, as base64, below the size at which an action’s payload is kept apart as the invoking app’s content, which another app could not read.