Have a look through this thread, heaps of suggestions
http://community.boredofstudies.org/showthread.php?t=228949
Personally, I used Dead Poets Society - excellent film for belonging (particularly in terms of identity, relationships, acceptance, exclusion, potential of an individual to challenge/enrich... basically every key term in the rubric), but quite popular, so use with caution. I also did We Are Going by Oodgeroo Noonuccal/Kath Walker, which is a lovely short poem on the spiritual significance of land to Aboriginals, cultural identification etc. - absolutely packed with techniques, and easily related to various ideas of belonging.
I recommend choosing a poem for your 2nd related so you can keep your analysis/paragraph for that component of your essay short and sweet. Try to vary your text types, so if you're doing a poem as your core, avoid using a poem for your related. That way you're able to show off more techniques and different styles of analysis.
Good luck!