On Japanese fan-sites (at least, ones I visited between 2001 and 2007), the most common designator for fanfic was 'shousetsu' (小説). I occasionally saw it written out in kana as ファンフィック (as an English loanword).

Similarly, the designation for "fanart" or "fanart gallery" was more often simply "e" (絵)　(pictures) than say, ファンアート etc.