Unless there is a specific limit on file sizes set by the institution there is no limit on the size of files you can upload to the server, although the size of the file you can upload depends on your connection speed. The server opens a connection for a fixed period of time and so the size of the file you can upload depends on amount of data you are able to transfer in that time.

One thing to remember when putting large files into your account is the kind of connection that the person viewing any shared files/assets might have. If they have a slow connection speed then viewing large files will inevitably take longer than smaller ones.