Back Structuring for Quicker Saving

Not sure if this is a support item or a me not doing it right item, so bear with me.

I like having reference material in my projects. Photographs of places, flora and fauna, lots of stuff, all neatly nested into thematic folders and close to hand should I need them.

The issue is this seems to massacre the ‘backup project’ option when I close Scrivener, my paranoia about secure file closing meaning I always quit this way. For example, my current project is taking about 3 minutes to close.

My question is, can anything be done (by me) to speed this process up, or do I simply have to accept it as a consequence of having lots of images nested away in a project?