Can I give my customer a dropbox folder (share) where he can put some JPG (one or more) and then get the brightsign unit pull the file and show it as part of a presentation.
Yes, you can. The easiest way to do this is using the media rss feed feature.
1) Upload images to the Public folder on your dropbox account. Right-click on every image, select "Copy public link" in order to generate a url.
2) Create an xml file in text editor (for example notepad++)
This faq has sample image rss feed, so you can see the structure and how an xml file should look like:
Specify the necessary tags and urls to images which reside in the Public folder on your dropbox account. Save xml file and upload it to the Public folder on your dropbox account.
3) Create a presentation in BrightAuthor, add Media RSS widget to a playlist. You need to click on the other tab, under media library, then drag the Media RSS icon into your playlist. You'll be asked to add your feed, and enter your url.
Right-click on the xml file in the Public folder, select "Copy public link", double click on the Media RSS object in a presentation, paste a url to xml file, save and publish a presentation to a brightsign unit.
4) When you want to update the images (to display new content), you need to upload new images to the Public folder, edit xml file to tell the unit to download new content. You need to update urls in the xml file. And you need to change the <guid> number in every item. Every content is stored in player within this unique guid. When you want content to be changed, you must change the guid tag in xml file. The changing of the guid tag is what tells the unit to download a new file. If you update the file name and url, but don't change the guid, then the new file won't be downloaded.
In this faq, there's some more info:
Not sure about the intent of the OP, but in my view, the biggest benefit of using Dropbox to display a folder of images is that you can quickly, easily, and painlessly manage frequent changes to the displays simply by adding and removing images from the folder, without the need to manipulate RSS feeds or playlists.
I use this to display graphics on computer monitors throughout my store simply by using the default Pictures screensaver that every computer has built in. I just change the images in my dropbox folder which is synched on all the other computers.
As far as I know, BrightSign does not offer the ability to simply play a folder of images. It would benefit greatly with this ability and would likely be a simple thing for the engineers to implement.
I use Rokus in several locations that display a Flickr set that I can easily update for this same purpose, so maybe that offers an option, though it is slightly more work to manage images on Flickr than in a folder on a disk. I believe there may be a channel available for the Roku to display from Dropbox, but haven't had a chance to look into it recently.
There's also a feature in the Brightsign Network service called Live Media. It lets you add images, plus a title and description (optional), and you can then use that as a feed in a Brightauthor project. Once published, users would just make changes to the feed on the web site, and it would be automatically updated on the player.