hi.

nginx.conf:
client_max_body_size 42m;


php.ini:
memory_limit = 64M
post_max_size = 40M
upload_max_filesize = 32M

it works fine for me with that settings. I havent speficied any timeout settings you used.
Have you edited php.ini for php-fpm? If not - default upload file size is 2M