Graphics does not render converting to PDF

Hi,

I am trying to convert a DocBook article (XML) into a PDF through the
Apache Cocoon and the standard stylesheets that I have downloaded from
the sourcefourge. The problem is that the images included in my
article does not render. I have tried with different file formats such
as JPG, GIF, EPS, PNG but reached no successful conversion.

Besids Apache Cocoon, I tried Jade but it does not render my images,
too. Please, help me resolve this conversion problem that I
experience.

-- 
Ferad Zyulkyarov
Dokuz Eylul University
Dept. Of Computer Engineering
35100 Bornova, Izmir - TURKEY
tel: +90 (0)555 3721637
e-mail1: 
e-mail2: