Hi Lise,
Sounds like a lot of work to rename the files and quite messy on the left pane. I think “Image management” is really a topic that needs to be handled. Eventually by managing what you do automatically: rename all image attachment names to <01> to <99> or more… and of course hide all this in the left pane 
I gave a +1 to a feature request that’s going in the right direction: Allow hidden folder for pictures: 
Maybe you should too if it meets your needs.
You might be interested by this one too: Use the current note name in the attachment subfolder name