I inserted an image to my report. When I call the report in my form (Oracle Forms), the image does not appear (just a gray field appears) . I have not encountered such an error in my other reports. What could be the reason of it?
If Reports Builder version is 9i or higher (you did tag the question with the "Oracle10g" tag, but I don't know whether you're talking about the database version or Developer Suite version) then your reports are deployed on the web. It means that they are ran from the IAS which also means that images you're displaying must be located on the IAS.
If you can see it when running the report on your own PC (during development), it is OK because - when you start the OC4J Instance, it acts as your web server.
Therefore, copy the image to the IAS. Which directory? I can't tell, talk to your DBA. I guess that placing it into the same directory that contains .REP files should work.