I agree with Kore.
The GD functions, that ez3 is using (like imagecreatetruecolor) need GD 2.0.
If you have an older version installed, you will not get the image working (talking about version 3.3).
ezPublish 3.2 MIGHT work with a lesser GD version, as there was a new imagesystem introduced in 3.3. Can someone at ez confirm this?
ez... do you really need the truecolor functions of GD? ;) See my bug report.
ImageCreateTrueColor() is required to handle conversion from JPEG (mostly truecolor) and some PNGs (can be truecolor). If not we would have to convert from true color to a palette based (max 256 colors) which will require dithering, and trust me you don't want dithered images on your site.
The second thing to consider is that there has been lots of bugs in earlier GD versions, if you want something stable I would recommend the latest one.