Add a RewriteRule for WordPress multisite - wordpress

Question

I have a brand new WP multisite network (v 3.5.1) on sub-directories. I'm getting an error with the images, where the subsites won't display them properly, but they are being uploaded correctly. I'm pretty sure all I need to do is add the correct RewriteRule to the .htaccess file in the main site, as such:
When an image is called from anywhere in the site, the URL is: example.com/subsitename/assets/sites/#/imagename.jpg. I want to change it so that the image actually pulls from: example.com/assets/sites/#/imagename.jpg, where subsitename, #, and imagename.jpg are all variables.
It seems like this should be really simple, but I'm having a hard time finding the right syntax or an example of someone else who has solved this issue. Does anyone know the proper RewriteRule I would add?
My current .htaccess file contains this:
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]

Answer 1

Try this instead:
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [L]
# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^[_0-9a-zA-Z-]+/(wp-(content|admin|includes).*) $1 [L]
RewriteRule ^[_0-9a-zA-Z-]+/(.*\.php)$ $1 [L]
RewriteRule . index.php [L]
</IfModule>
# END WordPress