Made a database consist of several files
Most popular reason of not implementing some usefull features (like attach any file, custom icons, etc) is that database file will be big and a lot of time will be needed to upload/download it from cloud during synchronization.
So, my proposal is to split database to several files. One for current database, second - for attached files storage, 3rd - for custom icons and so on. Or some another combinations. I.e. separate the data which can be changed / accessed frequently (cards text) from data, which is stable (attached files, etc.)