it’s possible on https://l10n.xwiki.org to contribute not only by performing translations, but also by uploading screenshots corresponding to some translation key. Performing this upload is currently limited by a right granted only to committers: by default it’s reserved to administrators, mainly to avoid abuse I think.
IMO it would be good to allow people who do not have the technical knowledge or the time to become committer, to contribute to XWiki by uploading the screenshots. Each screenshot added to a translation can help other translators to find back the right translation in the context.
Now I don’t know if we should allow everyone to perform those uploads, or if we should introduce a “XWiki Translator” status whenever people submitted some translations that got merged.