[TASK] Module icon for TYPO3 7 (stick to visual identity)

New background respects concept from @7elix:
https://twitter.com/7elix/status/537601034110369792

Change-Id: I4dff048302a606b74a1e9216ef4d34031109916e
Reviewed-on: http://review.typo3.org/34670
Reviewed-by: Xavier Perseguers <xavier@typo3.org>
Tested-by: Xavier Perseguers <xavier@typo3.org>