I'd vote for such a feature suggestion.
Preferences vs recommendations as to how a company uses Vault, I have to say where I am currently Preferences win.
With that said, I recall yrs ago when first introduced to Vault via our local VAR that they recommend only keeping files on your hard drive that you are actively working on and not use it to store anything you work on that is in Vault.
To each their own but I prefer doing just that. Even through out the day if there is the slightest chance something other than the machine I am working on ends up on my local pc, I'll check everything in, manually delete the hard drive contents thru Inventor's open window (this allows me to delete files that may still be in Inventor memory but are not actually open) then I re-get the model. Depending on what stage of the work load, I will only get 3D models. Towards the end I then pull down idw's. That reminds me, idw's do end up in the same folder as their iam or ipt files used to generate them.
After seeing your screenshot once more that sparked this suggestion that perhaps you've got more than you need on your pc. That would be another reason to want to see the thumbnails, if your pc has accidentally become a backup for Vault storage hehe.