A common asked question by customers and colleague-developers is what’s the max size for Media Library items since they are imported in the database in Sitecore 5.3. The answer on this question is quite easy: 16 Mb is the predefined absolute maximum for the RequestLength of a .NET defined in the Web.config:
 2385   <!–
 2386    httpRuntime Attributes:
 2387     executionTimeout=”[seconds]” – time in seconds before request is automatically timed out
 2388     maxRequestLength=”[KBytes]” – KBytes size of maximum request length to accept
 2389     useFullyQualifiedRedirectUrl=”[true|false]” – Fully qualifiy the URL for client redirects
 2390     minFreeThreads=”[count]” – minimum number of free thread to allow execution of new requests
 2391     minLocalRequestFreeThreads=”[count]” – minimum number of free thread to allow execution of new local requests
 2392     appRequestQueueLimit=”[count]” – maximum number of requests queued for the application
 2393    –>
 2394   <httpRuntime maxRequestLength=“16384“ executionTimeout=“600“ />
Altough Sitecore has defined 16 Mb as maximum, I would recommend you to instruate the customer to upload files with the maximumSize of 8Mb. This because of backwards compatibility to older browsers may stop the request after 8Mb…
When you’ve got larger files, provide the customers another way to upload. Let them send you a CD or allow them to upload it to a FTP server. After that you’re simply able to place the file in the /upload/-folder. Directly in the right folder(you have to create ‘m) or move them afterwards in the content tree.
Hope this helped…
Have a nice day 
