Screenshot image files should ideally be put in the assets/ directory (which you'll likely need to create) in the root of your SVN checkout. This will be on the same level as tags/ and trunk/, for example. Alternatively, screenshots can be put in the directory of the tagged stable release (trunk/ or the stable tag directory) (the old way). The assets/ directory is preferred since the screenshots won't be packaged in the plugin's release zip files, saving unnecessary bloat for each download. Learn more from the feature's announcement post.
Will require updating the svn-push command to move the assets directory to the level above trunk directory.
Via FAQ:
Will require updating the
svn-pushcommand to move theassetsdirectory to the level abovetrunkdirectory.