Does customizing the title of a file in a showcase also change that file’s name in my Dropbox?
No. If you customize the title of a file in a showcase, the name of the original (or "source") file in your Dropbox account remains the same. Customizing a file title in a showcase does not change metadata for the source file in any way.
Does a showcase use Dropbox storage space?
No, a showcase does not use additional Dropbox storage space. Only the files within the showcase use your storage space.
Files that weren’t previously stored in your Dropbox account go directly into a folder in your account called Showcase uploads. Files that already exist in your Dropbox account, but that you uploaded from another source (your downloads folder or somewhere else), also go directly into Showcase uploads. The only files in your showcase that don’t get stored in Showcase Uploads are files that were in your Dropbox account already and were uploaded to your showcase directly from your Dropbox account.
Do I have to keep files in my showcase synced to my Dropbox account?
Only the owner (or creator) of a showcase can edit it.
However, if you have shared files in your showcase, anyone you've shared those files with can edit them. Those changes would then appear in the showcase.
Will a showcase work on a phone or tablet?
Yes. If you share a showcase with someone, they'll be able to open and view it on any device: computer, phone, or tablet. All images and text will appear, regardless of the device.
Note: You can't currently create or edit a showcase on a phone or tablet.
What if I edit the source of the files that are in my showcase?
If you edit one of the files that's shared in a showcase, those changes will reflect in the showcase itself. Anyone who views, opens, or downloads the files in that showcase, will also see those changes. In this way, a showcase works much like a Dropbox shared folder: those with access will always see the latest copies of the files.