How do I put a new wallpaper on my Android 4.3 device? I've got an image I would like to make the wallpaper on my tablet.

When I go into Settings:Device:Wallpaper:Home Screen I have to select from one of the following:


Gallery
Live wallpapers
Wallpapers


The image I want to use is in my Dropbox.  Gallery appears to have some capability to sync with Dropbox, but I don't see any way to sync just a single file.  I have gigs of stuff in my Dropbox and don't want to wait (or waste flash) trying to sync everything over to my tablet for just one file.

Gallery doesn't appear to have any other capability to import files?!

I've tried some things directly from Dropbox.  I try tapping on the image and it brings up some kind of image viewer which doesn't seem related to Gallery.  When I long tap, I am given the options: "Share", "Favorite", "Delete", "Rename", "Move" and "Export".  The only one that seems potentially useful is "Export", however it brings up a list of apps, none of which is Preview.  It does have "Save to SD card" but I also don't know how to use an image on an SD card as a wallpaper!

I tried exporting it to my scrapbook, and from there it says the location of the file is:

/Android/data/com.dropbox.android/files/scratch/Camera Uploads/Galaxy.jpg


But this doesn't help me!  Strangely, from the Scrapbook there is also a "Link" button which says I can "Complete action using" and one choice is Gallery, but when I select that, even though I appear to be in the Gallery, the image still doesn't show up in the Gallery when I try to set the wallpaper.  Strangely, there is a menu option to "Set as" which says I can set it as my wallpaper, but when I select that it wants me to select what part of the image to use and shows me a portrait shaped rectangle to resize.  But I want to use the whole image!  Why can't I use a landscape image as a landscape wallpaper when my tablet is in landscape mode?

I tried going directly to the file system, but I can't find where wallpaper or gallery images are stored.  I tried doing a search by my file manager will only display the first 500 images, and these are all images from other apps.

This seems like it should be such a simple thing!
Dropbox is making it seem more complicated than it really is. Unlike on the PC version of Dropbox, the files you see in the Dropbox app aren't actually stored on your tablet. It's just a list of files you could download. When you view the file from Dropbox, it downloads it temporarily into Dropbox's private storage area, and then temporarily gives the app you choose access to the file.

Just click "Save to SD card". That actually downloads the file to your tablet, and  saves it permanently in a storage area that other apps have access to. After that, the image will show up in Gallery, probably in its own "Dropbox" album.