So as of a bit over an hour ago, we've entered the Final Freeze in preparation for the release of Ubuntu 15.04.
As usual, this means that you should refrain from uploading any seeded package which doesn't contain a release critical fix. If you're unsure about whether you should be uploading a package or not, please get in touch with the release team in #ubuntu-release.
Unseeded packages will still get auto-accepted until the bot is turned off shortly before release.
As for images, we're expecting the first run of candidate images to happen late tomorrow before most of us leave for a weekend of travel.