From SmashWiki, the Super Smash Bros. wiki
The Smash Service was a free feature provided by Nintendo on Super Smash Bros. Brawl via Nintendo Wi-Fi Connection. Each day, a new custom stage, new screenshot, and new replay is sent to those who have the feature activated. These are subsequently deleted by the end of the day.
On June 30, 2009, Nintendo stopped accepting new submissions, but continued to send out current submissions. The service was later discontinued entirely.