There are a few guidelines that are to be followed for uploading files. Currently there are restrictions on size and file type.
  Size: < 10MB
  Files: swf, jpg
In the future you may be able to upload more file types.

Your flash file will be kept on the server for a maximum of 30 days. If it is accepted to be shown on FlashStuf, it will be moved there within the 30 days. However if it is not accepted it will either be deleted immediately or kept until the 30 days is up.