I looked all over the net and wasn't able to find this answer anyway, so I looked into the nginx source files and it's very easy.
Simply modify the file located at [b]src/http/modules/ngx_http_autoindex_module.c[/b] and then compile.
Change these lines:
[b]#define NGX_HTTP_AUTOINDEX_PREALLOCATE 50
#define NGX_HTTP_AUTOINDEX_NAME_LEN 50[/b]
to whatever you want, such as:
[b]#define NGX_HTTP_AUTOINDEX_PREALLOCATE 100
#define NGX_HTTP_AUTOINDEX_NAME_LEN 100[/b]
And then compile and restart nginx. That's it !!!