the [URLCONTROLFILE] token is a direct replacement option for the [FILE] token in your form.html template files

[FILE] will render a Repository Upload control which allows the user to upload a new file to the server. It also mangles the filename, inserting a Guid between the filename and the extension which allows files with the same name to be uploaded and not overwrite an existing file. It also provides a small measure of security as the resulting filename on the web server will be impossible to guess.

[URLCONTROLFILE] will render a Core UrlControl, which allows a user to upload a new file, select an existing file from the web server, or enter a URL for the item. The filename is not changed and the user can elect which web folder to write the file to

So, if you want to take advantage of the Core UrlControl and it's options, just edit your form.html file and replace [FILE] with [URLCONTROLFILE]

Similarly, you can replace [IMAGE] with [URLCONTROLIMAGE] to use a Core UrlControl for Image uploads