misc: add static trisquel-wallpaper file and instructions.

helpers/DATA/trisquel-wallpapers/README.md

@@ -0,0 +1,26 @@
+# trisquel-wallpapers
+This folder centralize on the package-helpers repo the final wallpaper for
+the release.
+
+The final artwork should come from trisquel-packages/$VERSION/trisquel-wallpapers
+repository, make sure to review helper on the designed stage prior to
+release, so it uses right artwork when released.
+
+This should be copied with something like this:
+
+```
+cp $(find DATA/trisquel-wallpapers/ -name $CODENAME.*) \
+    warty-final-ubuntukylin.jpg
+```
+
+Helpers using this image should be identified using the tag:
+
+* `#STAGE-5-DESKTOP|ARTWORK`
+
+To ease identification.
+
+## Final wallpaper format
+Please note that the final wallpaper artwork file could be in JPG or PNG
+form (or any other format), make sure to make the necessary test to confirm
+that the format specific file is not an issue on your desired package helper
+use.