This has been mentioned on the mailinglist:
SHtml.fileUpload and CRUDify

Although there is a method uploadField_? in the BaseField class, this method has no effect on CRUDify. It would be nice, if CRUDify would automatically generate a form with enctype="multipart/form-data", whenever the underlying model contains at least one field, that is marked as upload-field.

I added a patch, that implements the above behaviour. Let me know if you need more.