Does your film need that something extra?
Is there a sound or image you do not have?
Can you not get the music quite right for the mood?
Try these links to find your needed 'extra effects'.
NEN Gallery
The E2BN / NEN Gallery is a community resource, built and maintained by the education community for the education community.
The gallery is a growing collection of high quality materials copyright cleared for use in teaching and learning. There are currently around 52,000 image, audio and video resources covering a wide range of topics relevant to the curriculum.
All of the resources in the gallery are archived at the highest quality available so they can be used on whiteboards, printed materials, animations and for any other educational application. Medium resolution versions of every file are also made available for review and preview.
This is a fantastically extensive library of music and sounds that is free for use in schools across the UK.  You must be on a school IP address to access this resource.  You can then search for relevant music for your film by mood, emotion, genre, time, movement and many more.  A wonderful much under used resource that can give that something extra to any animation.