Personally, I find this slogan quite good: it has a clear call to
action, mentions the goal of the contest (to help Wikipedia by
uploading photos), and will be true when we push it onto the projects
:-)) However, as this is quite an important change and might have a
huge impact, I would like to get a go-ahead from you--and also maybe
see some better ideas if you have them?

As mentioned above, I'd like to push the new banners on-line when we
break the record; which, in general estimates, might happen somewhere
between September 15 and September 20. This would give us about two
weeks to translate the phrases into the 37 languages we use for our
current banners.