Gdtyjr

I am trying to convert an existing book from plain PDF output to ebook format for online publishing (and doing some reformatting in the process, but that's another question).

I have images in the part page (thanks to @peter-wilson for that).
Problem is those images do not appear in tex4ebook output, without any error/warning.

Full (current) header of my book follows:

documentclass[10pt,ebook,italian,onecolumn,oneside,titlepage,extrafontsizes]memoir
usepackage[italian]babel
usepackagegraphicx
usepackage[utf8x]inputenc
usepackage[T1]fontenc
usepackageucs
usepackagemakeidx
usepackagequotmark
newcommandgqt[1]tqtscshape #1
newcommandstarsbegincenter * * *\ endcenter
%
makeatletter
def@partimage
newcommandpartimage[2][]gdef@partimageincludegraphics[#1]#2
renewcommandprintparttitle[1]parttitlefont #1vfil@partimagevfilgdef@partimage
makeatother
%
setlengthcftpartnumwidth2em
%
authorMauro Condarelli
titleCronache della Nuova Terra
begindocument
%
frontmatter
maketitle
%
mainmatter
chapterstylecompanion
%bookCronache della Nuova Terra
tableofcontents
%
partimage[width=210pt]old_mage.jpg
partIn cerca di un Mondo Nuovo
%
%
chapterLa Missione
%
%scene: 'Prologo I'

La Pianta non era certo imponente, somigliava a una verza troppo cresciuta, alta quasi un metro e mezzo e larga altrettanto, grandi foglie verde pallido sormontavano un tronco corto e tozzo dal quale partiva un robusto peduncolo che portava a una grossa zucca adagiata sulla sabbia pulita.par
...
%end scene
%
%end chapter
%

backmatter
appendix
%
%
enddocument

Problem, as said, is image (old-mage.jpg, in this case) simply vanishes leaving no visible trace.

I'm using a plain: tex4ebook -c tex4book.cfg Cronache_della_Nuova_Terra.tex to compile; contents of tex4book.cfg follows:

Preamblexhtml 
CoverMetadatathano.jpg
ConfigureAddCssblitz-lite.css
DeclareGraphicsExtensions.svg,.png,.jpg,.pdf
begindocument
EndPreamble

Any hint welcome