nginx serve static - images, js, css and proxy node.js server
This makes sense to me. You can add a few more directives, though.

In-memory caching of file metadata

Nginx has an in-memory cache for file metadata, which can improve performance. Here's a sample config:

open_file_cache max=10000 inactive=120s;
open_file_cache_valid 60s;
open_file_cache_min_uses 2;
open_file_cache_errors on;


Sendfile

Nginx supports the syscall sendfile, which, as I understand, can directly spit bytes on disk into the network, without intermediary reading into ram, which is obviously faster. Here's an article about sendfile and co, and a basic config:

sendfile on;
tcp_nodelay on;
tcp_nopush on;


events

Outside of the server {} block, there are a few settings you can configure.


epoll on linux; if you're on a different OS consult the manual
multi_accept is generally recommended, and causes the worker process to accept as many connections as possible.


Here's a config:

worker_processes auto;

events {
  use epoll;
  multi_accept on;
}


I'd recommend looking further into things, for example by searching "nginx static performance" or similar, there are many articles. These are what show up from the top of my head. I don't see anything wrong with your config as a base, though.