Hello Nicolas,

>> I'll revise my patch in this weekend. thanks.

I've split my work into these three commits:
  0001-ox-html-add-figure-and-table-numbers-to-HTML-caption.patch
  0002-ox-add-dictionary-entry-for-numbered-figures.patch
  0003-ox-add-Japanese-translations-for-figures-and-tables.patch
  (enclosed in the attachments)

I've also pushed them to my github repository:
  git@github.com:yoshinari-nomura/org-mode.git
  branch: tab-and-fig-number-to-ox-html

Please check the commits.
I'm willing to revise them again if needed.

Thanks for your great effort to tidy-up my rough work.

Regards,
--
Yoshinari Nomura
https://github.com/yoshinari-nomura

commit a82e712c3d60d8b58e2cffe13d5cbcdfa25ede24
Author: Yoshinari Nomura <nom@quickhack.net>
Date:   Sat Jun 29 15:06:49 2013 +0900

    ox: add Japanese translations for figures and tables
    
    * lisp/ox.el: (org-export-dictionary): Add Japanese translations for
    figures and tables

commit faced47cb6d049cbb4b6323556543bd86e32884d
Author: Yoshinari Nomura <nom@quickhack.net>
Date:   Sat Jun 29 15:02:41 2013 +0900

    ox: add dictionary entry for numbered figures
    
    * lisp/ox.el: (org-export-dictionary): Add "Figure %d:" entry
    in the same manner with "Table %d:".

commit 793f69627fa290c95d41c0af9792fdafdda98b06
Author: Yoshinari Nomura <nom@quickhack.net>
Date:   Sat Jun 29 14:44:52 2013 +0900

    ox-html: add figure and table numbers to HTML captions
    
    * lisp/ox-html.el: (org-html--has-caption-p): New function.
    (org-html-link--inline-image),
    (org-html-table): Prepend ordinal number to caption.
    (org-html-link): Make numbered link by counting captioned figures and tables.