When you generate RTF documentation from within EA, you have the choice of setting the image type to:
-EMF
-WMF
-GIF
-JPG
-PNG
-Bitmap
First step, I would try both EMF, or WMF first - as they are scalable.
Next, my question to you, if one or the other still does not work, are ANY of these types showing up in your RTF document in OpenOffice? Do any show up in Word?
I a similar problem here (and we ALL use Word), I would perform a documentation export, and it would appear correct on my machine - I'd email the RTF to my team - no images...

Well, there is a checkbox option - lower right-hand corner of the settings dialog, titled: "Embed Diagrams in Document". I had it off

, and of course, when I emailed the RTF, I forgot the individual files.
That fixed my problem, however I do not know how OpenOffice would handle that setting, you have to try it yourself.